Previous in Forum: Car Owner   Next in Forum: Grease Making
Close
Close
Close
Page 1 of 2: « First 1 2 Next > Last »
Guru
Hobbies - HAM Radio - New Member Hobbies - Model Rocketry - New Member

Join Date: Jan 2007
Posts: 792
Good Answers: 51

Perplexing Car Problem

10/14/2011 10:50 AM

My friends car has some baffling issues which a few of us have not been able to solve yet. The car is an Audi with 5 cylinders although I don't have more specifics of the car on hand.

The main symptom of the car is it won't start, but when you release the key and stop trying to start it, the engine starts running BACKWARDS for a second and then dies with a puff of smoke out of the air intake.

The car is fuel injected and the timing is electronic and has no manual adjustments.

My friend has already done a lot of tests and checks and replaced parts but no luck, the ones I can think of I will list.

  • The order of the plug wires has been triple checked by multiple people.
  • The timing alignment marks for the timing belt and valve cams has been checked and confirmed.
  • The spark timing has been checked both with a timing gun for piston #1 and also my friend has a multichannel scope which he connected sensors to all plug wires and also to the hall sensor and also to the cam position sensor.
  • Thinking it might be the computer, my friend replaced it.
  • The fuel injectors have been replaced.
  • The gear that drives the distributor has been replaced.
  • The coil has been replaced and the correct voltages have been verified.
  • The compression for all cylinders has been checked.
  • The fuel pressure has been checked.

The engine does not start or run backwards or start to turn backwards if you disconnect the coil.

I am sure I missed a number of things that were checked and this is really just a summary, and I am sure my friend checked things I don't even know about.

All the timings and everything checked so far has been right on spec and yet obviously something is wrong.

We are looking for possible ideas of what could be wrong or other tests that should be performed on the car.

Register to Reply
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be Good Answers:

These comments received enough positive ratings to make them "good answers".

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Guru

Join Date: Dec 2010
Posts: 1894
Good Answers: 44
#1

Re: Perplexing car problem

10/14/2011 11:13 AM

After such a lengthy intro, I hesitate to ask...

How do you perceive the engine to be running backwards? A starter motor will not run backwards so I really cannot fathom how this is perceived.

It sounds to me like you have the timing 180 degrees out. Some engines will still attempt to run in this configuration (especially non-interference engines). The backfiring out of the intake is indicative of the intake valves being at least partly open when they should be closed and the charge escapes through there. In most (I don't know about all engines, so that's a caveat) engines it is entirely possible to line up the cal marks for timing to 180 out. The major difference being (typically) is that number one piston is at BDC instead of TDC when the timing is aligned.

I am not sure about a five banger, but a six will also allow this situation with the distributor alignment...it all goes hand-in-hand quite nicely until you try to actually start the engine.

Register to Reply
Guru
Hobbies - HAM Radio - New Member Hobbies - Model Rocketry - New Member

Join Date: Jan 2007
Posts: 792
Good Answers: 51
#5
In reply to #1

Re: Perplexing car problem

10/14/2011 11:26 AM

I think what is happening is that when you try to start the engine, fuel is being pulled through the cylinders and then pushed out the exhaust. For some reason when you stop cranking the engine over this fuel in the exhaust manifold is running the engine backwards for a second.

The normal timing is about 8deg BTDC when starting, but he can interface with the computer and set it to 12deg BTDC for diagnostic purposes but the engine does the same thing either way.

My friend checked TDC of each piston by placing a rod through the plug hole and turning the engine with a wrench until each one was at the highest position. He then placed a mark on on the flywheel for TDC for each piston with the piston number. He also placed a mark at 12deg BTDC. With a timing gun we can confirm that the plug is firing on the correct timing mark and shifts correctly when the computer settings are changed this is also confirmed by the scope.

Since timing is before tdc as it is with most engines, I would think that if you started an engine turning backwards it could keep turning backwards as long as you have fuel.

The starter motor turns the engine in the correct direction, you can clearly see it turning one direction while trying to start and then when you release the key it starts going the opposite direction.

Register to Reply
Guru

Join Date: Dec 2010
Posts: 1894
Good Answers: 44
#35
In reply to #5

Re: Perplexing car problem

10/14/2011 2:49 PM

The the timing does not have a very wide range where the engine runs smoothly. If your timing is set 12 degrees before top dead center it would then need to be set 24 degrees after top dead center in order to be running backwards. This is all very improbable. The dieseling of the engine after shutdown is confusing the issue of bad timing or misplaced spark.

Did the ballast resistor get replaced in all of this? You may want to check its condition and verify the inductance of your coil as well.

Register to Reply
Guru
United States - Member - Member Engineering Fields - Electrical Engineering - Electrical Construction

Join Date: Apr 2010
Location: Mid Western USA - The Corn Belt
Posts: 1439
Good Answers: 58
#2

Re: Perplexing car problem

10/14/2011 11:16 AM

Good Morning Frank,

An Audi with 5 cylinders, that is the problem, you've misplaced a cylinder somewhere

Having said that the timing is electronic and not adjustable, the first thing that comes to my mind is the ignition module (assumed this module controls timing).

Back in the day (late 70's) I had a 225 slant 6 that gave similar symptoms after I removed and reinstalled the distributor.

Sorry I can't provide more guidance, it's been years since I was under a hood for a major repair.

There are several mechanic gurus here so hopefully help will be forthcoming.

Good Luck!

__________________
The first 5 days after a weekend are always the hardest................................
Register to Reply
Power-User

Join Date: Mar 2011
Location: Ground Zero of the Pompous and self important....Washington DC
Posts: 416
Good Answers: 8
#4
In reply to #2

Re: Perplexing car problem

10/14/2011 11:19 AM

Audi actualy DID have a five cylinder engine that far back (at least as early as the later 70's that I know for a fact, a friend had an Audi 5000 with a 5 cyl in it)...as did Mercedes.Only the Audi 5 cycle was gasoline and the Mercedes was a diesel.

Register to Reply
Guru
United States - Member - Member Engineering Fields - Electrical Engineering - Electrical Construction

Join Date: Apr 2010
Location: Mid Western USA - The Corn Belt
Posts: 1439
Good Answers: 58
#8
In reply to #4

Re: Perplexing car problem

10/14/2011 11:30 AM

I realize that, my comment was in jest

__________________
The first 5 days after a weekend are always the hardest................................
Register to Reply
Guru

Join Date: Dec 2010
Posts: 1894
Good Answers: 44
#11
In reply to #8

Re: Perplexing car problem

10/14/2011 11:35 AM

surely you...oh...yeah

Register to Reply Off Topic (Score 5)
Guru
United States - Member - Member Engineering Fields - Electrical Engineering - Electrical Construction

Join Date: Apr 2010
Location: Mid Western USA - The Corn Belt
Posts: 1439
Good Answers: 58
#14
In reply to #11

Re: Perplexing car problem

10/14/2011 11:44 AM
__________________
The first 5 days after a weekend are always the hardest................................
Register to Reply Off Topic (Score 5)
2
Guru
Hobbies - Fishing - New Member

Join Date: Jun 2008
Location: Raleigh, NC USA
Posts: 13529
Good Answers: 467
#3

Re: Perplexing car problem

10/14/2011 11:18 AM

Here's a guess:

Has the timing chain/belt been replaced, or the engine been rebuilt?

Here's one more thing to check if it hasn't been. Have them make sure that the timing mark is set at TDC on #1 cylinder on the intake stroke. If everything was put together at TDC on the exhaust stroke, it will appear to be completely normal, but it will be 180° out of whack. His plugs will be firing on the exhaust stroke. There will partial detonation, and could explain the backwards sputter.

__________________
Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety. Ben Franklin
Register to Reply Good Answer (Score 2)
Guru
Hobbies - HAM Radio - New Member Hobbies - Model Rocketry - New Member

Join Date: Jan 2007
Posts: 792
Good Answers: 51
#6
In reply to #3

Re: Perplexing car problem

10/14/2011 11:28 AM

The engine was not rebuild and the timing belt was not replaced. He was driving it and it started to sputter and died and he had it towed to the garage where it now sits and does what it does.

Register to Reply
Power-User

Join Date: Mar 2011
Location: Ground Zero of the Pompous and self important....Washington DC
Posts: 416
Good Answers: 8
#7
In reply to #6

Re: Perplexing car problem

10/14/2011 11:30 AM

First have the timing checked....including that cam timing....I bet its off significantly.

Register to Reply
Guru
Hobbies - HAM Radio - New Member Hobbies - Model Rocketry - New Member

Join Date: Jan 2007
Posts: 792
Good Answers: 51
#9
In reply to #7

Re: Perplexing car problem

10/14/2011 11:32 AM

We have checked the timing multiple times by multiple people in multiple ways, as of course that was everyone's first thought.

Register to Reply
Guru

Join Date: Dec 2010
Posts: 1894
Good Answers: 44
#13
In reply to #6

Re: Perplexing car problem

10/14/2011 11:43 AM

The distributor gear was replaced. That must be verified. The timing could be off any number of degrees mixing the intake and exhaust strokes for any number of cylinders. It sounds classic for a timing problem.

You also state that the timing has been checked with a timing light. How can you do this if the engine won't run? The engine must be running without retarded spark around 750-850 RPM for this to happen.

Register to Reply
Guru
Popular Science - Weaponology - New Member Safety - ESD - New Member Hobbies - Fishing - New Member

Join Date: Sep 2006
Location: Near Frankfurt am Main, Germany. 50.390866N, 8.884827E
Posts: 17996
Good Answers: 200
#54
In reply to #3

Re: Perplexing car problem

10/15/2011 3:45 AM

You get a GA from me as well for a good point.

But "just in case", (I don't really think that it is the case here) I must relate a tale of about 1976 of a friend/colleague of mine who had the same problem on a 4 cylinder Ford engine. He asked me to look at it after 3 days of perplexing problems and when I checked I found that he had fitted a new cam shaft and the new camshaft had a different firing order to the original one......swapped some plug leads and it started immediately.....

1) Check the firing order by removing all plugs and using a long screwdriver check that the pistons rise in the firing order expected.......2 minutes work.......

2) Then check that as the distributor rotates, that the plug lead of the "rising" cylinder is the one the rotor is just moving past in the distributor cap.....

Its amazing how simple checks like this can find and fix many such problems......

It seems that some manufacturers actually make different cams for different reasons (I have no idea why) and his original cam was not "standard", when the new cam was installed.......

.....and I know its a very long shot, but what else can you check?........

Best of luck.

__________________
"What others say about you reveals more about them, than it does you." Anon.
Register to Reply
Power-User

Join Date: Sep 2008
Posts: 208
Good Answers: 4
#84
In reply to #54

Re: Perplexing car problem

10/17/2011 6:15 PM

The 4 cylinder Ford engines from about 1960 onwards did have a firing order of 1243 instead of the "normal" firing order of 1342.

I also think the ignition timing might be out 180 degrees thus firing at the end of exhaust stroke instead of the end of compression.....just mark the rotor position, lift the distributor up, turn the rotor 180 degrees and bolt down again.

Register to Reply
Guru
Popular Science - Weaponology - New Member Safety - ESD - New Member Hobbies - Fishing - New Member

Join Date: Sep 2006
Location: Near Frankfurt am Main, Germany. 50.390866N, 8.884827E
Posts: 17996
Good Answers: 200
#94
In reply to #84

Re: Perplexing car problem

10/18/2011 3:56 AM

They were both.....had an experience with that, see an early post of mine in this blog.....never heard a reason why that really explained it either......

__________________
"What others say about you reveals more about them, than it does you." Anon.
Register to Reply
Guru

Join Date: Oct 2008
Posts: 42294
Good Answers: 1662
#10

Re: Perplexing Car Problem

10/14/2011 11:33 AM

I infer, from what you say, that the vehicle just decided to not start one day? As in, "out of the blue"?

That would mean that the owner did nothing/adjusted nothing/collided with nothing/replaced nothing/had no one replace or repair anything prior to the no-start condition. Is this true?

Just to confirm: someone has observed that the direction of rotation of the crankshaft reverses itself when the key is released to the run position, from start.

I'd suggest that you sit your friend down at the keyboard and let him tell the story. This is no different that having six eye-witnesses to a crime all give different descriptions of the criminal.

Register to Reply
Guru
Hobbies - HAM Radio - New Member Hobbies - Model Rocketry - New Member

Join Date: Jan 2007
Posts: 792
Good Answers: 51
#12
In reply to #10

Re: Perplexing Car Problem

10/14/2011 11:39 AM

He may sit down and write something although I figured I would search for ideas. I have worked with him on the car a couple of times, and while I don't know everything I have a good idea of what is going on.

He was driving the car it died on him and was towed to where it is now with the symptoms it has now. Things have been replaced since but none of them have changed the symptoms.

I personally as well as others have visually confirmed multiple times that the engine cranks one direction and then upon release of the key runs the opposite direction. It does so quite reliably actually.

Since I know we have check just about everything having to do with timing and cams and what not, I am more looking for the what did we not check or over look.

Register to Reply
Guru

Join Date: Oct 2008
Posts: 42294
Good Answers: 1662
#15
In reply to #12

Re: Perplexing Car Problem

10/14/2011 11:44 AM

I'm starting to believe that this may be an interference engine and the valves are bent.

Can you confirm the engine's valve clearance specifications?

Register to Reply
Guru
Hobbies - HAM Radio - New Member Hobbies - Model Rocketry - New Member

Join Date: Jan 2007
Posts: 792
Good Answers: 51
#19
In reply to #15

Re: Perplexing Car Problem

10/14/2011 11:52 AM

I don't know if it is interference engine or not I will ask my friend this evening, but I do know the compression of all cylinders check out.

We also did a simple check of covering the exhaust with our hand while cranking and it does build pressure. We also connected a gauge to a port on the exhaust manifold and while the exhaust is not being covered no pressure or vacuum is built up.

Register to Reply
Guru

Join Date: Dec 2010
Posts: 1894
Good Answers: 44
#21
In reply to #19

Re: Perplexing Car Problem

10/14/2011 11:58 AM

The compression check worries me if this actually is a timing issue. You shouldn't have accurate compression if the valve timing is off...

If you are getting partial firing and only a small amount of backfiring through the intake you may be only a couple of teeth off on the distro.

Why did he replace the distributor gear to begin with? Was it worn or showed signs of damage? If it was damaged then the driving gear on the associated cam may also be damaged and is changing the timing after each revolution...that would make it hard to keep up and cause a lot of head scratching.

Register to Reply
Guru
Hobbies - Fishing - Old Salt Hobbies - CNC - New Member United States - US - Statue of Liberty - New Member

Join Date: Mar 2007
Location: Rosedale, Maryland USA
Posts: 5198
Good Answers: 266
#22
In reply to #15

Re: Perplexing Car Problem

10/14/2011 11:58 AM

That's my thoughts also valve problem. Compression from a valve not opening is forcing engine to turn backward when the key turned off.

__________________
Life is not a journey to the grave with the intention of arriving in a pretty, pristine body but rather to come sliding in sideways, all used up and exclaiming, "Wow, what a ride!"
Register to Reply
Guru

Join Date: Dec 2010
Posts: 1894
Good Answers: 44
#16
In reply to #12

Re: Perplexing Car Problem

10/14/2011 11:47 AM

It's "trying" to run backwards to match the inaccurate timing of the valves. One or two cylinders reverse the rotation momentarily to match the valve timing. It's not actually running backwards, just rotating backwards.

If it were running backwards, then the backfiring from the intake would have a flame front involved like the exhaust.

Register to Reply
Guru
United States - Member - Member Engineering Fields - Electrical Engineering - Electrical Construction

Join Date: Apr 2010
Location: Mid Western USA - The Corn Belt
Posts: 1439
Good Answers: 58
#18
In reply to #16

Re: Perplexing Car Problem

10/14/2011 11:49 AM

Exactly!!!

__________________
The first 5 days after a weekend are always the hardest................................
Register to Reply
Power-User

Join Date: Mar 2011
Location: Ground Zero of the Pompous and self important....Washington DC
Posts: 416
Good Answers: 8
#25
In reply to #12

Re: Perplexing Car Problem

10/14/2011 12:49 PM

If it were 180 degrees out of time or near it....it will do some bizzare stuff. and still have compression

And if the distributer was out and replaced....it all assumes the cam timing didn't jump that much.....a stuck tensioner can allow it in an instant.

How old is that timing belt, how many miles are on it? (The Belt)

I've had a belt lose teeth on the highway before...because you are really getting noplace....make sure the cam is in the proper place on the proper stroke.

The crank turns twice for every ONE rotation of the cam.

Make sure the distributer is indexed correctly after that ( a few cars let them go in backwards). Make sure the plug wires are also in the right holes adn right order.

I know you have done some or all of this before....but when you are up against a wall , take a few steps back, and start on this fresh, making no assumptions. Maybe you missed something simple.

Register to Reply
Guru
Hobbies - HAM Radio - New Member Hobbies - Model Rocketry - New Member

Join Date: Jan 2007
Posts: 792
Good Answers: 51
#26
In reply to #25

Re: Perplexing Car Problem

10/14/2011 1:09 PM

I agree about doing stuff more than once, and actually a lot of this stuff especially timing related things, my self and another friend didn't believe the owner of the car. We each had to check it on our own to see that everything did line up and was correct. This includes the timing marks that relate to the timing belt.

So three people who ourselves work on our own cars often, have separately checked much of anything timing related because we had to see it for ourselves to believe it was correct. I personally have changed a number of timing belts and distributors on cars in the past so it isn't anything new to me nor to any of us.

As far as I can tell everything lines up and the plugs fire exactly when they should. I know people on here are going to keep going back to timing related issues, as I would do the same from reading this post.

What I am looking for is things that we simply did not think of.

Register to Reply
Power-User

Join Date: Mar 2011
Location: Ground Zero of the Pompous and self important....Washington DC
Posts: 416
Good Answers: 8
#27
In reply to #26

Re: Perplexing Car Problem

10/14/2011 1:41 PM

Well you have compression, timing, fuel and ignition. (but you already knew that)

One of those 4 has to be wrong.... or happening at the wrong times.

Compression implies valves and rings are good enough.

You have to be sure that the cam and distributer is properly indexes as other sensors are going to be off on fuel delivery if they aren't....and affects the distributer timing as well.

Fuel....well, it relies on the previous all being correct....as this is fuel injection.

And spark, you say the timing light says its where it should be. But one of those is clearly not what it seems.

Register to Reply
Guru
Hobbies - Fishing - New Member

Join Date: Jun 2008
Location: Raleigh, NC USA
Posts: 13529
Good Answers: 467
#28
In reply to #26

Re: Perplexing Car Problem

10/14/2011 1:59 PM

The one thing that hasn't been replaced is the distributor itself. The prior misfiring was likely due to a problem with spark. Getting a spark, and getting a proper spark are two different things.

If that plastic distributor gear was worn, it could have created slop in the distributor shaft. This can also cause erratic behavior. If the coil is good, I'd be taking a closer look at that distributor. It doesn't take much slop in the shaft to make it not run right.

__________________
Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety. Ben Franklin
Register to Reply
Guru
Hobbies - HAM Radio - New Member Hobbies - Model Rocketry - New Member

Join Date: Jan 2007
Posts: 792
Good Answers: 51
#30
In reply to #28

Re: Perplexing Car Problem

10/14/2011 2:18 PM

I don't think the plastic gear was worn but was replaced anyhow. We have visually watched the dist shaft turn as we turned the engine by hand all is smooth. Also if this was off the plugs wouldn't fire in the correct order but from looking at a scope and timing gun they do.

From a different question, my friend also told me he did a leak down test on the cylinders, that and a compression test which all came out good, which should rule out most valve issues.

Register to Reply
Guru

Join Date: Jun 2011
Location: Mossel Bay, SA
Posts: 777
Good Answers: 21
#71
In reply to #26

Re: Perplexing Car Problem

10/17/2011 3:24 AM

Can the distributor only be fitted in one position? I don't want to dwell on the obvious, but....

Register to Reply
Guru
United States - Member - Member Engineering Fields - Electrical Engineering - Electrical Construction

Join Date: Apr 2010
Location: Mid Western USA - The Corn Belt
Posts: 1439
Good Answers: 58
#17

Re: Perplexing Car Problem

10/14/2011 11:48 AM

Just to clarify, when you say that when you let the key go the engine turns in reverse, I assume you mean, in reverse 2 or 3 revolutions, correct?

EDIT: Cuba Pete covered this.

__________________
The first 5 days after a weekend are always the hardest................................
Register to Reply
Guru
Hobbies - HAM Radio - New Member Hobbies - Model Rocketry - New Member

Join Date: Jan 2007
Posts: 792
Good Answers: 51
#20
In reply to #17

Re: Perplexing Car Problem

10/14/2011 11:56 AM

The engine runs for more than 2 or 3 revolutions and sometimes revs quite high going backwards. At first my friend didn't know it was going backwards, although now that he knows it is going backwards he tries to shut it off as quick as he can.

A lot of smoke does come out of the air intake when it goes backwards.

Register to Reply
Power-User

Join Date: Mar 2011
Location: Ground Zero of the Pompous and self important....Washington DC
Posts: 416
Good Answers: 8
#29
In reply to #20

Re: Perplexing Car Problem

10/14/2011 2:16 PM

I'm curious how its managed to do this several times without jumping time....

This will usually cause timing to jump on anything with a timing belt to jump. At the tesion is now becomes the slack side (with no tensioner) and the belt it pulled tight against the ensioner allowing slack to occur, and with slack, a cance for th belt to jump.

Personal experience with timing belts ( Honda ) its they are very unforgiving when attempts at reverse rotation are made....and even timing CHAIN cars with overhead cams....are very intollerant of any reverse rotation even once. (Mercedes being one example). Those are both well built engines with histories of 2-300K+ miles not unusual.

No doubt frustrating....particularly since you and your friends aren't new to cars or engines.

Register to Reply
Guru
Hobbies - HAM Radio - New Member Hobbies - Model Rocketry - New Member

Join Date: Jan 2007
Posts: 792
Good Answers: 51
#42
In reply to #29

Re: Perplexing Car Problem

10/14/2011 3:36 PM

I can't say I have a lot of experience with engines running backwards. I can say that I have looked at the timing marks on the pulley's a number of times and everything lines up so the belt does not appear to have jumped.

Register to Reply
Guru
Hobbies - Fishing - New Member

Join Date: Jun 2008
Location: Raleigh, NC USA
Posts: 13529
Good Answers: 467
#23

Re: Perplexing Car Problem

10/14/2011 12:17 PM

The gear that drives the distributor has been replaced.

I think something went wrong with either the distributor or gearing to begin with, and either it hasn't been corrected yet, or a new problem was created when replacing the gear. If it's getting spark and it's getting gas, there are only a couple of things left. Either some computer or sensor is out, or the timing is way off. Gas plus spark = combustion=running engine, but they have to happen simultaneously.

__________________
Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety. Ben Franklin
Register to Reply Score 1 for Good Answer
Guru
Hobbies - HAM Radio - New Member Hobbies - Model Rocketry - New Member

Join Date: Jan 2007
Posts: 792
Good Answers: 51
#24
In reply to #23

Re: Perplexing Car Problem

10/14/2011 12:34 PM

For the sake of explaining the problem, I left out a little bit in terms of the distributor gear. Months prior to this issue my friends car was running but would randomly miss on random cylinders. He found that the gear the drives the distributor is plastic and people have had issues with it. He got a brass replacement gear and installed it, the car did run after this gear was put in but still had the same problem of missing.

This is also true for the computer, the fuel pump and the injectors, the car was running with all of these new parts but still had the same original missing issue until it died and refused to start with what it has now. I don't believe any new parts have been installed since the car died.

I sent the owner of the car a link to this post, I don't know if he is reading it or not.

Register to Reply
Power-User

Join Date: Apr 2007
Posts: 414
Good Answers: 19
#49
In reply to #23

Re: Perplexing Car Problem

10/15/2011 12:29 AM

Agreed. It looks like an ignition timing problem. The high parts cost of European cars makes testing by replacement expensive, but it may be the only option that will solve the problem in the owner's lifetime.

Register to Reply
Guru

Join Date: Dec 2008
Location: Cd. Juarez, Chihuahua, Mexico.
Posts: 1023
Good Answers: 69
#31

Re: Perplexing Car Problem

10/14/2011 2:24 PM

Hello

You said that you checked compression using your hand at the exhaust, and tested suction at the intake the same way; well, this is not reliable at all, get a compresion gauge and check each cilinder against specs to clear all doubts about the valves.

If they are OK (hopefully they are), then replace any ignition module that receives the signal from the computer and that sends it to the ignition coil, because all the simptoms described by you correspond in all to what my old CJ5 was doing 2 years ago.

It fooled me for a while, because I was expecting square pulses at the input of the ignition module, but they were 55 Khz bursts, each corresponding to a spark pulse.

I put a new module and it (the module) worked exactly the same way, except that the incoming bursts had slightly higher amplitude (about 20%)... that was it! it ran like a champ!.

I was surprised that such a little change in amplitude made the difference, but it's been running great since then. Oh, and no more ocassional miss fires.

Regards

__________________
No hay conocimiento ni herramienta que sustituya al sentido comun.
Register to Reply
Guru
Hobbies - HAM Radio - New Member Hobbies - Model Rocketry - New Member

Join Date: Jan 2007
Posts: 792
Good Answers: 51
#33
In reply to #31

Re: Perplexing Car Problem

10/14/2011 2:33 PM

The compression was checked with a compression gauge and a leak down test was also done with the correct equipment. The hand over the exhaust was just to make sure that pressure was escaping at the exhaust more as a double check of valve timing and possible cat blockage, nothing to do with compression.

The ignition module/hall sensor has been looked at as a suspect, and has been traced on a scope alongside the firing of the coil. All the pulses are where they should be in regards to this and the coil is firing at the correct timings which should rule this out.

Register to Reply
Guru

Join Date: Dec 2008
Location: Cd. Juarez, Chihuahua, Mexico.
Posts: 1023
Good Answers: 69
#39
In reply to #33

Re: Perplexing Car Problem

10/14/2011 3:17 PM

I used a scope too, and everything was where it should be, didn't bother to check compression though; the problem was preplexing to me too.

It took a little longer to get it done, because I, based on my measurements, refused to replace the ignition module at first.

Swapping modules with another vehicle, or get a loaner module, or even spend a little money on a new one, is something I highly recommend.

Just give it a try, then come back ant tell me if it worked.

__________________
No hay conocimiento ni herramienta que sustituya al sentido comun.
Register to Reply
Guru
Hobbies - Fishing - New Member

Join Date: Jun 2008
Location: Raleigh, NC USA
Posts: 13529
Good Answers: 467
#32

Re: Perplexing Car Problem

10/14/2011 2:33 PM

Does it have a coil, or coil packs?

Problems with coil packs seem to be very common.

__________________
Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety. Ben Franklin
Register to Reply
Guru
Hobbies - HAM Radio - New Member Hobbies - Model Rocketry - New Member

Join Date: Jan 2007
Posts: 792
Good Answers: 51
#34
In reply to #32

Re: Perplexing Car Problem

10/14/2011 2:33 PM

Just one coil and a distributor, no coil packs, had a car and a boat with coil packs not a fan of them either.

Register to Reply
Power-User

Join Date: Mar 2011
Posts: 238
Good Answers: 14
#36

Re: Perplexing Car Problem

10/14/2011 2:54 PM

The solution to this may lie in the fact that when the key is released the car runs backward. There is a different electrical signal going to the ignition module during start position and run position of the key. I have had several Fords that when the ignition module dies, it still works in start position but will not keep running when the key is released. I would see if there is spark while turning the key that is not there after the key is released (while the engine continues to turn for another half revolution or so with no spark) or vise versa (maybe no spark while in start position but gets spark when key is released) to get a sudden spark and turn backwwards. I would also double check that the plugs are firing near TDC of the compression stroke and not the exhaust stroke.

Register to Reply
Guru
Hobbies - HAM Radio - New Member Hobbies - Model Rocketry - New Member

Join Date: Jan 2007
Posts: 792
Good Answers: 51
#37
In reply to #36

Re: Perplexing Car Problem

10/14/2011 3:05 PM

While I myself didn't verify this but did ask, my friend says he used a spark gap device that goes inline with the plug wires and said it had a healthy spark both while cranking and when in the run position. The scope he has and the pickup devices he is using measure the high voltage and you can see on the trace that the spark voltage remains the same.

Register to Reply
2
Guru

Join Date: Feb 2005
Location: New York
Posts: 578
Good Answers: 16
#38

Re: Perplexing Car Problem

10/14/2011 3:09 PM

I think you should tell your friend its about time to bite the bullet and get a new car.

__________________
Kaplin
Register to Reply Good Answer (Score 2)
Guru

Join Date: Dec 2008
Location: Cd. Juarez, Chihuahua, Mexico.
Posts: 1023
Good Answers: 69
#40
In reply to #38

Re: Perplexing Car Problem

10/14/2011 3:26 PM

Even tough I consider this a good advice, I wouldn't recommend biting any bullets, much less chew on them!.

In the other hand, I'm curious and would want to know what hapened to the mistery perplexing car. I hope that the OP is considered enough to post also a solution when he finds one.

__________________
No hay conocimiento ni herramienta que sustituya al sentido comun.
Register to Reply
Guru
Hobbies - HAM Radio - New Member Hobbies - Model Rocketry - New Member

Join Date: Jan 2007
Posts: 792
Good Answers: 51
#41
In reply to #40

Re: Perplexing Car Problem

10/14/2011 3:32 PM

I will post back once a solution is found.

Register to Reply
Guru

Join Date: Dec 2008
Location: Cd. Juarez, Chihuahua, Mexico.
Posts: 1023
Good Answers: 69
#75
In reply to #41

Re: Perplexing Car Problem

10/17/2011 9:31 AM

Hello Frank;

I think you are messing with several things wich are not the culprit. Sometimes, if you tweak too much other things, you won't be able to fix the problem even if you correct the original cause. Leave everything the way it was at the begining.

When I said that my Jeep exhibited the same simptoms "in all" I meant exactly identical, and there was a spark to every cylinder too. That part was the most perplexing to me, but I later learned that it (the spark) wasn't powerful enough to ignite the air-fuel mixture.

That was a result of the faulty ignition module, it wouldn't sustain the arcing when the plug was surrounded by the mixture.

Another no-fire case would be:

When you wrongly set the gap to a sparkplug, you always see a spark with the plug removed, but when you install the plug you have no ignition to that cylinder; now, I'm not saying this is your case, I just want to make clear that the presence of spark is no warranty of ignition.

The causes of this lack of igniting power may lie on the HV coil, the ignition module, a bad distributor cap, worn out cables or worn out sparkplugs (yes, they get to fail even if you keep 'em clean).

I passed thru this 12 years ago, but this time, when my module finally failed, I was expecting more life from it ( "can't be the f****'n truth, I just replaced it ten years ago !"); well my friend, I also learned that things are not ethernal.

Just replace the ignition module, I bet you a soda it will solve the mistery once and for all !.

__________________
No hay conocimiento ni herramienta que sustituya al sentido comun.
Register to Reply
Commentator

Join Date: Apr 2009
Posts: 94
Good Answers: 3
#43

Re: Perplexing Car Problem

10/14/2011 4:37 PM

Try the ignition switch. It probably isn't connecting while the key is turned all of the way. When its released it it briefly connects and fires the gas already in the cylinders.

__________________
"Never mistake intelligence for wisdom"
Register to Reply Score 1 for Good Answer
Guru
Hobbies - HAM Radio - New Member Hobbies - Model Rocketry - New Member

Join Date: Jan 2007
Posts: 792
Good Answers: 51
#44
In reply to #43

Re: Perplexing Car Problem

10/14/2011 5:12 PM

I found someone who had that problem while searching other forums. The scope readings and the spark gap show that the coil is in fact firing while it is cranking.

Register to Reply
Guru
Hobbies - Fishing - New Member

Join Date: Jun 2008
Location: Raleigh, NC USA
Posts: 13529
Good Answers: 467
#45

Re: Perplexing Car Problem

10/14/2011 5:52 PM

Frank,

Have your friend disconnect the fuel line, turn the key, and pump some gasoline into a clear plastic bottle. If he got a bad batch of gas with water in it, it would cause all of the problems you describe.

We've all been assuming that the gas itself is good.................maybe not.

I've had this happen to me.

__________________
Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety. Ben Franklin
Register to Reply Score 1 for Good Answer
Power-User

Join Date: Feb 2011
Location: New Zealand
Posts: 128
Good Answers: 5
#46

Re: Perplexing Car Problem

10/14/2011 10:56 PM

It sounds like a simple case of "coil robbing". This happens when the starter motor or the battery are not 100% and while the motor is being cranked by the starter motor, the voltage to the coil is insufficient to provide a strong pulse to the spark plug and so the fuel/air mixture does not burn.

When the starter stops drawing current from the battery, the battery can supply the coil with an increased voltage and a good spark results.

If that happens when at a stage where the flywheel can keep the motor turning so that a piston passes top dead center before the burning fuel expands too much, the motor will start normally.

However, if the key is released when a piston is on its compression stroke but the flywheel can only get it to the firing point but not over TDC, then it will run backwards for a brief moment.

Of course a 4 stroke motor cannot really run backwards so, if this happens, it will blow a bit of smoke out of the intake system and stop.

Register to Reply
3
Power-User

Join Date: Mar 2011
Location: Sydney . Australia
Posts: 409
Good Answers: 34
#48
In reply to #46

Re: Perplexing Car Problem

10/15/2011 12:10 AM

the above could be valid and worth checking

also , check if the timing gear has a key or splined shaft , has the woodruf key sheared , causing the timing gear to rotate on the shaft ?

when he checked the timing gear mark at TDC , did he also check if both valves were closed or was the crank 360 degrees out ?

Register to Reply Good Answer (Score 3)
Power-User

Join Date: Jun 2009
Location: Australia
Posts: 277
Good Answers: 45
#62
In reply to #48

Re: Perplexing Car Problem

10/15/2011 11:04 PM

A GA for mentioning cam timing and distinguishing this from the marks. Also a GA for The Wrench for the same point. If the original poster is correct in saying that the motor has ran backwards at high speed for a couple of seconds it surely must be that the exhaust cam has slipped considerably from where it should be and since the marks are in line then either the cam gear has slipped 180 deg or the cam shaft as slipped in the gear.

And on the matter of compression, if the exhaust valve timing has slipped back quite a bit, compression could be quite high and the new configuration would allow reverse running.

All the posts about wrong fuel or wrong ignition timing or computer problems would all support one reverse firing to two, forward dieseling or not starting but are not consistent with the reported sustained high speed reverse operation symptoms as above. One also needs to remember that the engine died while hot and running under load. The prior miss problem may well be unrelated and so not relevant - its certainly less important than the other diagnostic materials presented.

Register to Reply Score 1 for Good Answer
Guru
Hobbies - DIY Welding - New Member

Join Date: Apr 2008
Location: Bristol, Tennessee
Posts: 1176
Good Answers: 57
#47

Re: Perplexing Car Problem

10/14/2011 10:57 PM

I've come across a couple of vehicles that do not time to no. 1 cylinder. Check the book to see what cylinder to use.

__________________
mike k
Register to Reply Score 1 for Good Answer
Guru

Join Date: Oct 2008
Posts: 42294
Good Answers: 1662
#57
In reply to #47

Re: Perplexing Car Problem

10/15/2011 12:49 PM

Right! This one times to the #6 cylinder.

Register to Reply Score 1 for Good Answer
Power-User
Hobbies - CNC - New Member Engineering Fields - Mechanical Engineering - New Member

Join Date: Apr 2007
Posts: 162
Good Answers: 6
#50

Re: Perplexing Car Problem

10/15/2011 1:02 AM

orkra's thought about the not coming over TDC is somewhat common. Also someone mentioned the compression reading. What are the compression readings? They should be over 120psi, probably more like 160psi. Someone mentioned cam timing. The marks may be inline but the cam drive may have slipped. Check to see if both valves are open the same amount at TDC overlap. This is one crankshaft rotation past TDC compression stroke, one half rotation of the camshaft. The exhaust valve will be closing and the intake will be opening. Depending on the configuration of the motor, sometimes it would be as simple as putting a straight edge (a short ruler) on top of the valves or rocker arms of the # 1 cylinder and checking to see if this valve event really occurs at TDC. If the valves are hidden in the head somehow or it an OHC, over head cam, checking this may be more difficult.I think that is where the problem is. Also the compression reading should be a little low. Probably below 100psi. Many times people think that that is enough for the motor if it has lots of miles on it, and it's " just a little worn" so they think the rings are worn but it is really the cam has retarded with wear of the timing chain, or the belt has slipped "jumped at tooth or two". Good luck!

Register to Reply Score 1 for Good Answer
Associate

Join Date: Sep 2011
Location: Ontario
Posts: 52
Good Answers: 2
#51

Re: Perplexing Car Problem

10/15/2011 1:43 AM

It happened to me once that a gas station attendant filled diesel in my tank instead of gasoline. I got almost all the way home, 10 miles, before the car died and it took me a while to figure out what had happened. please make sure it is real gasoline in the tank.

Another thing is the timing gear on the camshaft may have moved so it will look like the timing is OK when it is not. this could also be the case with the distributor gear.

Finally someone sugested that the timing may not be tied to cyl 1 on that car, that should definitely be checked out.

Good luck and let us know how it goes.

__________________
Fools rush in where wise men fear to go...
Register to Reply
2
Guru

Join Date: Oct 2009
Location: sometimes Wales,UK.. was Libya, now Oman!
Posts: 1715
Good Answers: 116
#52

Re: Perplexing Car Problem

10/15/2011 2:00 AM

have you asked Audi?

You mentioned a computer and its been replaced.... do you have an anti-theft device fitted to the car as standard? That is, the car will only start with the dedicated key?

It might be the computer/anti-theft is not recognising the key.

__________________
The square root of nothing is what you make it!
Register to Reply Good Answer (Score 2)
Commentator

Join Date: Jun 2011
Posts: 77
Good Answers: 8
#53

Re: Perplexing Car Problem

10/15/2011 2:12 AM

(OP) You have quite the mystery car there. I am surprised that you weren't able to find anything on an Audi forum somewhere. And yes, I did read all of the posts so I won't suggest you do something that you have repeatedly said you have done .

So in a word, your compression checks out, your cam indexing appears to be OK, you apparently have enough spark energy applied at an appropriate time, and you have fuel. The only thing I can think of (and you/he/others may have already checked this out) is the timing of and amount of fuel delivery. It may be possible that the fuel is being injected at the wrong time, causing the head scratching dilemma you are faced with. I would pull the injectors out and see what kind of spray pattern and volume you get, scope the injector signals to make sure their timing and duration are to spec. Good luck.

Register to Reply
Power-User

Join Date: Apr 2005
Location: Scotland
Posts: 157
Good Answers: 6
#55

Re: Perplexing Car Problem

10/15/2011 5:16 AM

I've had an Audi 90, 2.2SE car with 5 cylinder engine for the past 21 years and it still keeps up with a fast Imprezza going through the Scottish mountains..

From memory I had a similar problem a few years back which was caused by a faulty rotor arm in the distributor. Inside the rotor arm, there is a carbon supressor resistor and this had completely vaporised and the spark was getting to the rotor arm tip via the burnt carbon! Remove the rotor arm, look on the underside and you will probably see a burnt slot where the resistor used to live. The car still ran but was very hard to start and lost power. You can measure the resistance between the centre of the arm and the tip - should be between 600 and 1400 ohms. New rotor arms should still be easy to obtain.

Another similar fault, again in the distributer cap, was a hairline crack in the plastic which short circuited the centre HT terminal to the metal case of the distributor.

Two faults in the same area is worth your friend having a good look at the distributer rotor arm and the cap. If you need any other information on this Audi I still have the Haynes workshop manual. I had the timing belt off last month to replace the water pump and had no problem reassembling and resetting the timing.

Register to Reply
Power-User

Join Date: Dec 2010
Posts: 166
Good Answers: 4
#56

Re: Perplexing Car Problem

10/15/2011 6:42 AM

Check the crankshaft position sensor and associated wiring. A problem here could cause the ignition to fire where it "thinks" the engine is not where it actually is. Better living through computers. Garbage in, garbage out!

Register to Reply Score 1 for Good Answer
Active Contributor

Join Date: Dec 2008
Posts: 21
#58

Re: Perplexing Car Problem

10/15/2011 2:56 PM

Just a reminder to one or two posters. This engine does not have a crank position or speed sensor it uses a Hall effect sensor in the distributor. for both chores. It will use a conventional mechanical advance system within the distributor for advancing the ignition timing. I suggest something simple is wrong. Timing being the favourite. A 5 cylinder engine will not easily be put 180 degrees out of time as all cylinders fire at different engine positions. Only No 1 cylinder can be used for checking the timing. If the hall effect is broken by the metal segment in the distributor coming between the generator and receiver within the distributor at roughly a degree or two before top dead centre on no 1 cylinder it should fire correctly. I would take of the cam cover and check that at this position the back of the cams are against the lifters. Then manually check that each cylinders valves are on the back of the cam at the same time as a segment is just begining to cover the sensor and that the rotor arm is pointing to the correct cylinder in the distributor cap. Do not check these fundamentals at different times. All together. If these basics are correct it will start with fuel. Timing is not critical to starting, it may run like a dog but it will start. If you think the fuel could be seriously compromised and it would need to be serious to not start, then disconnect the fuel pump and try to start it on butane or propane; I used to use a big blow torch. Try to avoid using petrol poured in to the plenum etc as this could ignite easily if the engine backfires in to the inlet manifold. Is the car equipped with K jetronic or electronic injection?

Register to Reply
Power-User

Join Date: Jul 2007
Location: Melbourne Florida
Posts: 122
Good Answers: 2
#59

Re: Perplexing Car Problem

10/15/2011 3:43 PM

I once had a ford or maybe a chevy which ever. I had a problem whereas when I started the engine it would not start if I held the key in the start position but it would when I released the key to the run position. What I found was a bad starter relay. Not the solenoid but an additional relay. The way it worked was, when the key was switched to start the relay would close sending 12 volts to the coil and when switched to start it would send about 8 volts to the coil. It never tried to run backwards though. I agree that it does sound more like a timing issue or firing order.

Good Luck!

__________________
repeat problems can not be solved by the same way of thinking ( A. Einstein)
Register to Reply
Guru
Popular Science - Cosmology - Let's keep knowledge expanding Engineering Fields - Retired Engineers / Mentors -

Join Date: Dec 2006
Location: North America, Earth
Posts: 4373
Good Answers: 104
#60

Re: Perplexing Car Problem

10/15/2011 4:25 PM

We had a John Deer tractor that would run backwards when you turned off the key and then turned in back on before the engine died down. It was only a few strokes, though. High rpm backwards is not to be expected.

__________________
“I would rather have questions that can't be answered than answers that can't be questioned.” - Richard Feynman
Register to Reply
Power-User

Join Date: Feb 2011
Location: New Zealand
Posts: 128
Good Answers: 5
#61

Re: Perplexing Car Problem

10/15/2011 5:57 PM

I still suspect coil robbing. This would be exacerbated by the spark timing being a little too far advanced before TDC. An auto electrician can check that in about two minutes with a stroboscopic light. And in another two minutes will tell you if the starter motor is 'robbing the coil' by drawing so much current that the coil does not get sufficient voltage until the key start is released.

Please let us know the reason for the problem when you solve it. As you will. There is nothing very complicated in a reciprocating engine and the answer , when you find it, will be a simple one.

Register to Reply
2
Power-User

Join Date: Mar 2011
Posts: 117
Good Answers: 15
#63

Re: Perplexing Car Problem

10/16/2011 2:58 AM

I would be checking for a gear or timing belt pulley that the keyway is not aligned with the shaft keyway. If it was worn it may have been shifting timing for a while and causing the misfires and then the key broke completely, allowed the shaft to turn significantly perhaps 180 degrees but with it being a 5 cylinder I can imagine lots of positions that may eventually allow one cylinder to fire (or2) and then before it got completely around to that position, a 3rd cylinder that is many degrees after TDC fires and causes the reversal.

The gear that is bad may be on the camshaft where the new brass distributer gear meshes and therefore very hard to check visually without some head disassembly. Or it may be the one behind a harmonic balancer, etc.

I suggest this is not going to run until you have the basic mechanical timing correct. Many here have agreed on the timing as the likely problem. What I am offering is that the testing you are doing may be giving false indication of being right but that is based on some mechanical pieces still being good as new. My experience with all the other pieces is that it would really run crappy, but it would run.

__________________
For every action, there is an equal and opposite criticism.
Register to Reply Good Answer (Score 2)
Guru
Popular Science - Weaponology - New Member Safety - ESD - New Member Hobbies - Fishing - New Member

Join Date: Sep 2006
Location: Near Frankfurt am Main, Germany. 50.390866N, 8.884827E
Posts: 17996
Good Answers: 200
#64
In reply to #63

Re: Perplexing Car Problem

10/16/2011 3:33 AM

GA

I liked your post, it smacks of the type of possible problem the engine has.

__________________
"What others say about you reveals more about them, than it does you." Anon.
Register to Reply Score 1 for Good Answer
Guru
Hobbies - RC Aircraft - New Member Hobbies - Automotive Performance - New Member Hobbies - DIY Welding - New Member

Join Date: Jul 2007
Location: Fort Lauderdale Florida
Posts: 5708
Good Answers: 123
#126
In reply to #63

Re: Perplexing Car Problem

10/19/2011 12:55 PM

Not possible. If the camshaft to crankshaft is not correct, the OP will not have the compression he found. If a gear, sprocket, or hey slips once, it will only retard the camshaft from that point on. It can never regain its timing until it slips an entire revolution and returns to the original line up position.

__________________
Bob
Register to Reply Score 1 for Good Answer
Guru
Hobbies - RC Aircraft - New Member Hobbies - Automotive Performance - New Member Hobbies - DIY Welding - New Member

Join Date: Jul 2007
Location: Fort Lauderdale Florida
Posts: 5708
Good Answers: 123
#131
In reply to #126

Re: Perplexing Car Problem

10/19/2011 9:03 PM

Sorry, the key slips, not the hey.

__________________
Bob
Register to Reply
Power-User

Join Date: Mar 2011
Posts: 117
Good Answers: 15
#65

Re: Perplexing Car Problem

10/16/2011 4:05 AM

Please be aware that every timing shaft to gear or pulley must have some positive locking mechanism. Sometimes the shaft does not had a keyway that is cut completely along the shaft. It may be a half-moon cut into the shaft and completely covered by the gear or pulley requiring you to remove the gear or pulley to see if it is in the correct alignment. I am familiar with them being called woodriff keys but have also seen "D" shaped keys. Some evidence of metal filings may be present to give you a hint that it is the one with the failure.Also if it is the failed one it will likely be very hard to remove because of the remains of the key have lodged between the shaft and the normally round part of the pulley.

__________________
For every action, there is an equal and opposite criticism.
Register to Reply
Guru
Popular Science - Weaponology - New Member Safety - ESD - New Member Hobbies - Fishing - New Member

Join Date: Sep 2006
Location: Near Frankfurt am Main, Germany. 50.390866N, 8.884827E
Posts: 17996
Good Answers: 200
#66
In reply to #65

Re: Perplexing Car Problem

10/16/2011 5:00 AM
__________________
"What others say about you reveals more about them, than it does you." Anon.
Register to Reply
Guru

Join Date: Sep 2008
Location: Where the sun sets on OZ
Posts: 1366
Good Answers: 27
#67

Re: Perplexing Car Problem

10/16/2011 7:28 AM

My first thought was the ignition switch. I see "Catmandoo" has the same idea. My friends Audi of that vintage had a crappy ignition switch as well, 'though not these symptoms.

Should be able to 'hot wire' it to find out.

__________________
Where's the KaBoom? There should be a KaBoom!
Register to Reply
Commentator

Join Date: Dec 2010
Posts: 80
Good Answers: 6
#68

Re: Perplexing Car Problem

10/16/2011 9:19 AM

Hello. What happens if you pull the distributor and retard the timing one tooth ?

Register to Reply
Anonymous Poster #1
#69

Re: Perplexing Car Problem

10/16/2011 6:14 PM

a diesel engine can start in a counter rotation. the problem is that the starter only has enough power to charge and compress the fuel mixture, but not enough power to complete the compression cycle. when the key is tiurned off, the compression in the cylinders is making the motor turn in the oppisite direction. this is why it tries to start in the opposite rotation.

you need to trouble shoot the starter and the starter wiring includind the battery. the starter does'nt have enough power to rotate a high compression diesel engine.

i would take it to a starter/generator repair shop.

Register to Reply
Anonymous Poster #2
#73
In reply to #69

Re: Perplexing Car Problem

10/17/2011 7:29 AM

We are discussing a petrol engine here......DDDUUUUUHHHHHHHH

Register to Reply
Guru

Join Date: Aug 2010
Location: Melbourne, Australia
Posts: 740
Good Answers: 24
#70

Re: Perplexing Car Problem

10/17/2011 2:02 AM

A mechanic friend was telling me about one engine he had to re-build - He had to replace the head, pistons, con rods etc, etc

The Crankshaft gear driving the timing belt had a rubber insert molded between the outer (teeth) and inner (crankshaft mounting) - what had happened was that the rubber had separated from the metal allowing the valve timing to vary until pistons hit valves and the destruction was significant - he showed me the pulverised head (done by broken valves) and some of the pistons with holes in them where the valve heads had gone through ...... the owner had phoned when he noticed the first signs of trouble and was told to put it on a tray truck and transport it immediately to the workshop and under no circumstances to start the engine again ...... He chose to drive it to the workshop - fast along the freeway! He did not make it!!!!

Register to Reply
Member

Join Date: Sep 2011
Posts: 5
#72

Re: Perplexing Car Problem

10/17/2011 7:14 AM

Any chance the starter is wired backwards?

Register to Reply
Commentator

Join Date: Dec 2010
Posts: 80
Good Answers: 6
#74
In reply to #72

Re: Perplexing Car Problem

10/17/2011 9:03 AM

Hello.If i understand the OP the engine rotates backwards after the key is released from the start position.Second to wire most automotive starters backwards would require a positive ground or positive case ground.If this were the case the OP would not have fuel or spark.

Register to Reply
Member

Join Date: Sep 2011
Posts: 5
#76

Re: Perplexing Car Problem

10/17/2011 9:44 AM

Understood and it has been some time since I owned an audi (1985), but I believe they are isolated power lines for positive and negative for everything. Back then they didn't use the chassis for the negative ground. In theory the starter could be wired backwards. The control lines to the starter could be wired normally as, I think they carry on the power to the ignition. Overall I believe the car is 180 out of timing. I only suggested it as it looks like this has been beat to death and a fundemental item may have been overlooked.

Register to Reply
Commentator

Join Date: Dec 2010
Posts: 80
Good Answers: 6
#85
In reply to #76

Re: Perplexing Car Problem

10/17/2011 8:57 PM

Hello.My post was generic as i cannot find any specifics for the vehicle in any of the posts except for it is an Audi and a 5 cylinder. date of manufacture? model? cid or cc's ?europe or usa ?if usa federal emissions or california ? turbocharged ????????

Register to Reply
Power-User

Join Date: Mar 2010
Posts: 123
Good Answers: 3
#115
In reply to #76

Re: Perplexing Car Problem

10/18/2011 9:03 PM

Automotive starters run ALWAYS in the same direction.

Connecting + and - in either way.

Does that engine have hydraulic operated valves?

Register to Reply Score 1 for Good Answer
Guru
Hobbies - HAM Radio - New Member Hobbies - Model Rocketry - New Member

Join Date: Jan 2007
Posts: 792
Good Answers: 51
#77

Re: Perplexing Car Problem

10/17/2011 10:01 AM

There are too many comments to reply to, but I did read them all but will only comment to the ones I remember.

We checked for a healthy spark during cranking, and it is fine and at the correct timing and not 180 deg off as confirmed by watching the valve cams. It does not appear any keys have slipped or are off.

The ignition module was replaced as well as the cap and rotor and plug wires and plugs.

The compression is above 100psi I don't know the reading but it was within a few psi that the engine should be at per the repair book.

The gas in the tank is not very old, he did pull the fuel rail and measure the amount of fuel from each injector.

Everything we test and measure says this engine should be working, this is coming from people who work on cars. The owner of the car has a friend that used to work as a car mechanic, and he is also stumped.

I only pop in and out while my friend is working on his car, but I will let you know what it turns out to be if and when he fixes it.

Register to Reply
Power-User

Join Date: Feb 2011
Location: New Zealand
Posts: 128
Good Answers: 5
#80
In reply to #77

Re: Perplexing Car Problem

10/17/2011 11:22 AM

At the risk of appearing pedantic, I have to say that a healthy looking spark in the open air does not always mean the spark will ignite the mixture under compression. Tell your friend to check the battery voltage while cranking and while not cranking.

Register to Reply
Guru

Join Date: Dec 2008
Location: Cd. Juarez, Chihuahua, Mexico.
Posts: 1023
Good Answers: 69
#101
In reply to #80

Re: Perplexing Car Problem

10/18/2011 8:32 AM

Hi Oraka;

I hope such comment doesn't make pedantic, because I made the same observation earlier on this thread.

__________________
No hay conocimiento ni herramienta que sustituya al sentido comun.
Register to Reply
Power-User

Join Date: Mar 2011
Location: Sydney . Australia
Posts: 409
Good Answers: 34
#102
In reply to #101

Re: Perplexing Car Problem

10/18/2011 8:50 AM

Hey Yahlasit

your posts here have been good , you're a good clear thinker .

well done and best wishes

Register to Reply
Commentator

Join Date: Jun 2011
Posts: 77
Good Answers: 8
#81
In reply to #77

Re: Perplexing Car Problem

10/17/2011 4:53 PM

Hi Frank, just had a follow up question. You mentioned that the injectors were checked for volume, but have they the (injectors)been check for their timing? it may be continuous injection so it would be a moot point, but if not it could pose problems.

Register to Reply
Guru
Hobbies - HAM Radio - New Member Hobbies - Model Rocketry - New Member

Join Date: Jan 2007
Posts: 792
Good Answers: 51
#82
In reply to #81

Re: Perplexing Car Problem

10/17/2011 5:18 PM

They have not and is a suggestion I made to my friend early on before I posted the question to the forum.

What I don't understand however is how injecting at the wrong time could cause this issue. The fuel can only get pulled into the cylinder when the intake valve is open, so even if they were off the fuel would sit in the intake manifold till it got sucked in. I could see the engine running poorly from this, but not acting the way it is.

The engine is getting fuel, the plugs get wet and you can smell the fuel in the exhaust.

The latest test my friend is doing is to determine exactly at what angle of the cam shaft the valves open and close. While we can clearly see the cams are correct, and know the valves are opening and closing, he told me yesterday he has hydraulic lifters which shouldn't but could complicate things.

Register to Reply
Guru

Join Date: Aug 2010
Location: Melbourne, Australia
Posts: 740
Good Answers: 24
#83
In reply to #82

Re: Perplexing Car Problem

10/17/2011 5:59 PM

If the problem is as I suggested in 70 the valve timing could be a few degrees out but all the indications would say it was correct - everything else would be correct - the easiest way to check would be to look at a new timing belt crankshaft drive gear and note the relationship between the keyway and the timing mark then check the same on the fitted drive gear ...... by the way, depending on their construction the same could apply to the camshaft timing gear...... again all indications would appear and measure correct except the relationship between the keyway and timing mark on the gear.

Register to Reply
Power-User

Join Date: Dec 2010
Posts: 166
Good Answers: 4
#89
In reply to #82

Re: Perplexing Car Problem

10/18/2011 12:55 AM

If the plugs are wet with gasoline then it is definatly an ignition issue.

Register to Reply
Guru
Popular Science - Weaponology - New Member Safety - ESD - New Member Hobbies - Fishing - New Member

Join Date: Sep 2006
Location: Near Frankfurt am Main, Germany. 50.390866N, 8.884827E
Posts: 17996
Good Answers: 200
#95
In reply to #89

Re: Perplexing Car Problem

10/18/2011 4:01 AM

Sorry, it can still be timing of the spark in relation to the valves/engine. In fact, that is still my theory in spite of the fact that it has been checked according to the OP......I don't think that the test was made exactly enough, but that is just an opinion from thousands of miles away..... in Audi land!

__________________
"What others say about you reveals more about them, than it does you." Anon.
Register to Reply
Guru

Join Date: Sep 2008
Location: Where the sun sets on OZ
Posts: 1366
Good Answers: 27
#90
In reply to #82

Re: Perplexing Car Problem

10/18/2011 1:14 AM

The engine is getting fuel, the plugs get wet and you can smell the fuel in the exhaust.As mentioned by ORAKU a healthy spark in air may not equate to a healthy spark under compression. You say that the engine is getting plenty of fuel and the timing is right. A simple test is to remove the spark plug and then reconnect the lead and just lay the plug near the plug hole. This should result in a belch of flame as the plug ignites the fuel so choose your plug hole wisely. If this does happen then it would be a fair bet the ignition module is faulty. Nowadays cars use ignition modules that provide a type of spark that doesn't erode the plugs. In the bad old days we could just increase the gap in the plug to get a "hotter" spark to test the firing.As the above test is simple to do just try it.

__________________
Where's the KaBoom? There should be a KaBoom!
Register to Reply
Commentator

Join Date: Apr 2009
Posts: 94
Good Answers: 3
#78

Re: Perplexing Car Problem

10/17/2011 10:15 AM

I have never worked on a 5 cylinder engine. Does the distributer time to #1 cylinder or another? Just asking........ I haven't seen that mentioned.

__________________
"Never mistake intelligence for wisdom"
Register to Reply
Guru

Join Date: Jun 2011
Location: Mossel Bay, SA
Posts: 777
Good Answers: 21
#79
In reply to #78

Re: Perplexing Car Problem

10/17/2011 10:29 AM

See #58

Register to Reply
Power-User

Join Date: Jun 2009
Location: Australia
Posts: 277
Good Answers: 45
#86

Re: Perplexing Car Problem

10/17/2011 10:31 PM

I stick by my post that you have a valve timing issue if the symptoms are exactly as you describe - however if one or two of the symptoms are not correctly described have you considered the possibility of a "bad earth" or "bad sensor/connection" or the like.

For example, if you swapped out the computer and found this made no difference, then that would be the case if one of the wires to the computer were faulty as "swapping the computer" does not change the connections to it.

Short of checking every connection and wire carefully, it might be easier rig up a crude new ignition system, bypassing all but maybe the hall sensor. If the engine starts then you've isolated the problem to "ignition", if not then you've isolated it to "valve timing or fuel". I do not see anyway it can be fuel if the motor died "in traffic" (unless it was just refuelled), a I think you reported.

Register to Reply
Power-User

Join Date: Mar 2011
Location: Sydney . Australia
Posts: 409
Good Answers: 34
#87
In reply to #86

Re: Perplexing Car Problem

10/17/2011 11:39 PM

yes TrevorM

isolate a group of elements to narrow the scope of focus and keep doing so in ever decreasing circles until the culprit is found

some of the posts on ignition switch / ignition module have a feeling about them if valve timing is found to be correctly set up

Register to Reply
Power-User

Join Date: Mar 2011
Posts: 117
Good Answers: 15
#88

Re: Perplexing Car Problem

10/18/2011 12:24 AM

Request $5 donation for each members opinion, use the money to buy a donor car and start shotgun swapping parts until the donor car runs backwards.

Sorry, I thought it was time to insert some intentional humor.

__________________
For every action, there is an equal and opposite criticism.
Register to Reply Score 1 for Off Topic
Active Contributor

Join Date: Dec 2008
Posts: 21
#91

Re: Perplexing Car Problem

10/18/2011 1:59 AM

Some of these ideas floating around are crazy. The guy says the plugs are all sparking. It is not an ignition issue. It is clearly a timing issue. Just go back to basics and do what I said in post #58. Posters who have commented on woodruff keys etc are correct in pointing to a possibility that timing marks are not always reliable. Crank position marks are on the flywheel and should be checked against piston position through the plug hole on No1 cylinder only. With this mark established the valve timing can be checked very easily by observing the cams on the back when no 1 cylinder is firing and the valves are just on the rock ie, both just open when the engine is at TDC on the exhaust stroke. The reason the engine runs backwards is; when the key is released and power is shut of to the coil it issues a final spark as the current in the windings is cut - That's how the ignition generates sparks - It is this final spark that is allowing the engine to fire. If it occurs when a cylinder is coming up on the compression stroke but is in a before top dead centre position, it will push the engine backwards. Incidentally this also confirms the compressions are good. Finally, if you can't get your mates mechanics to get it going tell your mate he needs a decent mechanic. If he wants to buy me an air ticket from the UK and pay expenses I'll get it going for him in 30 mins max.

Register to Reply
Power-User

Join Date: Jun 2009
Location: Australia
Posts: 277
Good Answers: 45
#92
In reply to #91

Re: Perplexing Car Problem

10/18/2011 2:46 AM

Much of what you say is true but "ignition" can mean "timing" or "spark" or both, so care is needed in accusing someone of being crazy or wrong etc.

I agree with you (I think) - part of the problem is that there are a lot of symptoms and too many people ignore one or more of them - you for example seem to have ignored the symptom that the motor runs backward (fast according to one post) for a second.

That means its fires many times while running backwards, so that a single "switch off" generated spark makes no sense either. And if one runs the argument that continued backward running is a diesel effect, then that is inconsistent with starting a cold motor on good fuel.

If the symptoms are reported correctly, it seems the issue has to be a timing slip (of the valves) as I can't see that ignition slip could do it.

But, if not correctly reported I'd favour something not properly looked at yet i.e. a lose/poor connection combined with a computer somewhere. One obvious difference on the ignition side (in many motors) is the presence of a ballast resistor in the "not starting" ignition on position.

Register to Reply
Guru

Join Date: Aug 2010
Location: Melbourne, Australia
Posts: 740
Good Answers: 24
#93
In reply to #91

Re: Perplexing Car Problem

10/18/2011 3:33 AM

Be aware also that on some European cars No 1 cylinder is the crankshaft pulley end, on others it is the flywheel end - check your manual

Register to Reply
Register to Reply Page 1 of 2: « First 1 2 Next > Last »
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be Good Answers:

These comments received enough positive ratings to make them "good answers".

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Copy to Clipboard

Users who posted comments:

Andy Germany (16); Anonymous Poster (2); Beenaround (4); bob c (6); brich (1); bubbapebi (1); Catmandu (5); cherryvan (1); cuba_pete (6); dthomas16 (4); dvmdsc (2); Far (1); frankd20 (24); Gazu (2); grandpaw (4); harley (1); hatchera (2); Hilton (2); JIMRAT (5); JonathanG (3); jurie sa (1); Kaplin (1); KJK/USA (5); kramarat (6); lyn (3); mike k (1); Nothing is Impossible (7); Oraka (3); ozzb (1); richard harris (7); Smoothy (5); StandardsGuy (1); the wrench (1); tom (2); TrevorM (4); WAWAUS (4); Yahlasit (5)

Previous in Forum: Car Owner   Next in Forum: Grease Making

Advertisement