Jerking car...why?

I'd have said carburettor/aircleaner need cleaning, not forgetting all the breather pipes finlers and crap stuff which go to the rocker cover /crank case on modern engines.
Failing that, is the fuel high enough octane...?

Del

Hi Del,

Carb's been cleaned and the aircleaner's brand new. I don't know what a "breather pipes finlers" is. There are tubes that take vacuum from the engine. I had to replace one of them recently but the problem's been there before the tube failed.

In this model car, the air cleaner has a large, long tube attached to it. Attached to the tube (underneath) is something. I don't know what it is and the mechanic I've been taking the car to has never touched it.

I've been thinking of removing it entirely. Still, I'm not sure if that will solve it. I don't want to mess around with the engine since I don't know enough about them. I know the basics but that's about as far as I go.

finlers is cat talk for filters

I'm not familiar with that make of car, but the "something underneath" the air intake of the air filter housing is usually a duct to allow hot air off the exhaust manifold to enter the air intake, which helps the engine run better when it's cold. I wouldn't remove it, unless you live where it' always warm (which maybe it is in the Philippines). I have had a somewhat similar problem as you describe on an early 1970s MGB roadster and an 87 VW Cabriolet (Rabbit). If you let off the gas, the throttle plate on the MGB would close rapidly unless the carburetor dashpot (King's English for damper) was properly topped up with fluid. Properly filled, the dashpot allowed the throttle plate to close in a smooth manner, rather than "slamming shut." The VW has fuel injection, and there is no "dashpot" as such. but if you let off the gas abruptly, engine rpms will drop too low and it will sometimes stall. So you have to let off the gas gently, and it works fine. This is an indication of underdamping, same as the MGB. So on your car you need to look at whatever mechanism acts as a damper to keep the throtle plate or fuel injection version thereof from closing too quickly.

the throttle plate on the MGB would close rapidly...

Interesting. That could be one of the things I could ask my mechanic to look into. Thanks.

Check the motor mounts!

TMF

"Check the motor mounts!

TMF"

I like this answer. Check the motor mounts first.

Hmmm, I've never checked those. I don't know if the mechanic's checked them as well.

I'll have a look see tomorrow but would a loose mount cause the jerking? I mean, it doesn't feel like something's loose. The car just bucks like it's braking and releasing at half-second intervals.

"Hmmm, I've never checked those. I don't know if the mechanic's checked them as well.

I'll have a look see tomorrow but would a loose mount cause the jerking? I mean, it doesn't feel like something's loose. The car just bucks like it's braking and releasing at half-second intervals."

Check the motor mounts to rule them in or out.

If the engine is loose and raises up off of it's mount on one side, it will pull the accellerator cable with it, tugging on the carb or throttle assembly.

If the unconnected engine mount pulls on the acellerator cable as the engine is decellerating sharply.............. this could in turn pull on the accellerator cable and rev the engine making it torque back down into the mount....................... and a bucking bronco scenario develops.

It's not the valve caps or the tires.

Revving the engine while observing it's movement, or even putting the tranny in gear witht the engine off and pushing/rocking the car back and forth while observing the engine might help determine the condition of the mount...................... only one side has to be bad to cause issues, not both of them.

Check this issue first and either rule it in or out as a possible cause.

Your description seems more radaical than a carb or clutch problem............ or valve stem caps.

Bad motor mounts would allow the engine to move and roll excessively causing the various linkages to pull and push inappropriately. I have a car sitting outside that did just that until we replaced the mounts.

j.

If that car has a "points" distributor I would check the points clearance. This especially manifests when you try to accelerate up an incline and the car starts staggering.

It also occurs to me that you might have a bad clutch, especially one with an irregular disc surface that starts breaking loose and alternatively grabbing when you suddenly let off the gas.

j.

manifests when you try to accelerate up an incline and the car starts staggering

No, that doesn't happen. Going up an incline is a breeze. Going down is another story. Since I have to let off the gas to touch the brakes, the car starts jerking.

... alternatively grabbing when you suddenly let off the gas.

That's exactly what I have.

Interesting. And it seems to take us back to the vacuum idea. Just wondering...how is your oil consumption rate. Here's why I ask. Going down the hill your engine is engine braking...and also generating high vacuum in coast mode. Going up the hill under load...vacuum will drop. Now, whenever coasting (whenever vacuum at the manifold goes high), and if the valve tappet oil seals are badly worn, then oil can be drawn in along with gasoline through the carburetor. Other than to say, it's through the EGR (exhaust gas recirculation) system, I won't do into great detail...which you wouldn't understand anyway. What happens then, is that when the car is suddenly changed into coast mode (especially when the weight of the car is going downhill), so much oil enters the cylinders with the fuel mix that the car stumbles because the sparks cannot burn the oil-gas mixture fast enough. On the other hand, if the gas pedal is eased off slowly (going into coast mode) oil is drawn in more slowly...slow enough so that the engine can catch up burning the oil along with the gasoline. If oil consumption going downhill is great enough, this might show up as blue smoke exiting through the tail pipe. So there, you have one failure mode (one also more likely on 4cylinder engines) that matches exactly to the symptoms you have reported.

Now one way to check this out would be to tear down to the tappet seals (underneath the valve/tappet cover) and inspect directly. That is probably a job for your mechanic. Before doing that, you could also trace the EGR piping back from the carburetor to the EGR valve, and from there back to a canister near the bottom of the engine. (Refer to an after market manual as needed.) If you remove the canister, look inside. If you see heavy deposits of gunk inside (or in the tubing and or ports of the EGR valve) then that' an almost sure sign that oil is being drawn under high vacuum into the carburetor; and an almost sure sign of bad tappet seals...in probably several cylinders. As said before in another post, a good preliminary step would be to hook up a vacuum gauge to monitor vacuum during engine the various phases of engine operation. If you get an inexpensive test gauge, it will come with instructions and diagrams telling you how to do the test...what to look for in normal and abnormal engine function. You can set the gauge inside while you drive as well as under the hood. Having a passenger or helper to record vacuum readings will also be helpful. If you take it to a shop...be sure to ask them to do vacuum testing. Another quick test you can do is to run the engine at idle. As the engine idles, one by one remove and one spark plug wire at the plug and see what happens. Then replace the wire and go to the next. What you're looking for is differences between cylinders in how each responds when spark is removed. This will help give you and idea of the scope of problems inside the engine. Perhaps which cylinders might have been "damaged" by burning of bypass oil as per above.

"Now one way to check this out would be to tear down to the tappet seals (underneath the valve/tappet cover) and inspect directly."

Or you could just remove a spark plug, and check for oil deposits.

"Another quick test you can do is to run the engine at idle. As the engine idles, one by one remove and one spark plug wire at the plug and see what happens. Then replace the wire and go to the next. What you're looking for is differences between cylinders in how each responds when spark is removed. "

Did you forget to mention that that 25,000 volts is going to feel like an electrical shock?

Good point...the first one...maybe.

I forgot to mention (before you beat me to it), be sure to use insulated pliers, preferably one for boot removal. Thanks for the help.

and if the valve tappet oil seals are badly worn, then oil can be drawn in along with gasoline through the carburetor. Other than to say, it's through the EGR (exhaust gas recirculation) system, I won't do into great detail.

**Special note: Removing ignition cables as the engine is running is inherently dangerous due the potential of a 30,000+ volt shock and akin to holding the end of a long cable being whipped about by an elephant. Have three buddies each hold a wire and someone to film the event for review of correct firing order

This is an actual condition though I'm certain you are refering to the PCV and not the EGR...Right. Could the little ball be stuck eh?

The long and the short of it is attachment of and engine analyser and competent technician to operate.

Though without an engine analyser a check for this condition is far simpler than you have described also, the presence of ooze upstream of the PCV in the vacuum hoses etc.. Or a compression test, inspection of a spark plug or two may glean telltale sign of failed valve stem seals also.

You may not be aware of the many different valve lash settings and valve timings for this particular engine series which if a mix up were to occur could cause a contribution of symptoms though may not be the cause either.

Perhaps while he is holding that spark plug wire that is being charged with 20, to 30,000 volts he could just unscrew the spark plug at the same time?

And with any luck Vulcan can get a good video of it for all of us to watch.

This is an actual condition though I'm certain you are refering to the PCV and not the EGR...Right. Could the little ball be stuck eh?

No, I meant EGR...but you're right, oil can also be drawn through the PCV along with blow-by, especially upon "hard" deceleration. My point in emphasizing EGR - other than avoiding making things too complicated at once for our friend - was to give him the most direct means of checking, by looking first for the port at which recycled flow enters the carb, and then tracing back from there to EGR and whatever is upstream. I am not familier with Nissan 4cyl engines but typically there will be some point at which EG and PCV flow are combined before being drawn back into the fuel mixture at the carb. Sometimes this will be a canister of some kind on 4-bangers. The idea, then, is, once the recirculation path to the carb (or manifold) is identified, trace to any point at which uncontrolled oil might be entering during periods of low vacuum.

I am still convinced though, that the problem must be related to vaccum based on the description of the problem. It could be oil..., flooding, or fuel starvation related.

...oil enters the cylinders with the fuel ...

I don't notice my oil level decreasing (I usually check it everyday) so that might not be it. I'll see if I can find a vacuum gauge here. However, even if I did, I don't know how much is normal.

Regarding the spark plug cables test, I watched my mechanic do that. There's no difference in the reaction between cylinders.

I don't notice my oil level decreasing (I usually check it everyday) so that might not be it. I'll see if I can find a vacuum gauge here. However, even if I did, I don't know how much is normal.

Regarding the spark plug cables test, I watched my mechanic do that. There's no difference in the reaction between cylinders,

Thanks. So you know that based on the mechanic's test you have adequate cylinder balance...and almost certainly no electrical ignition problem...which leads us back to a fuel system problem.

The fact that you're not able to quickly discern oil (dipstick) level losses is not necessarily significant:

• After all, you're only seeing the bucking problem intermittently and for short periods during otherwise normal driving; the amount of overall oil "loss" during these events doesn't have to be much.
• The dipsticks measures oil reservoir depth in an oil pan in which the oil surface is spread out over a large area relative to the size of the stick.
• Normal, "Full" oil level as measured on the stick can vary up to an inch or more depending on engine and ambient temperature...which in the Philippines with its hot climate will tend to make Normal dipstick readings on the high side...
• (This might be a good time to advise...that if you're checking the dipstick every day, and possibly adding oil from time to time, you must be sure never to add oil unless the oil level reads very near, at, or below the "Minimum" mark on the stick. Do not add oil to bring the level to the maximum mark, or else when the engine comes to operating temperature, you will have an oil overfill condition: a condition which could contribute to the problem you are seeing.)

About checking the plugs--

It is true (as others have suggested) that oil fouling will sometimes be found by/when removing and inspecting plugs...mostly when oil control is a persistent rather than intermittent problem. Moreover, in your situation, checking plugs might not be a reliable indicator since, between the bucking episodes (assuming they are caused by oil) there will possibly or probably be sufficient time of acceleration and normal cruise driving during which normal ignition and fuel burn will be sufficient to burn off all oil...to clean the plugs. Therefore, the only infallible indicator of oil entering the intake will be visual inspection of oil paths into the intake...as indicated in the previous post.

What you might want to consider now is a little experiment: We can try to fault isolate vacuum-drawn oil problem by eliminating paths for oil circulation by disabling recirculation paths through the Carb or manifold.

First the PCV— Using any kind of clamp or clip without sharp edges (say an old style, push-on clothes pin) pinch of the PCV tube downstream of where it joins the PCV (valve). Then test drive the car (several miles should do it) and see how it affects you deceleration bucking problem. If no change, then PCV is not acting as a significant oil path during deceleration...just a blow-by vapours path, which is normal.

Next, EGR— Here we will disable any fuel contaminating oil by disconnecting the EGR intake tube from the Carb or manifold. At the port on Carb or manifold, you disconnect the EGR output tube and plug the Carb or manifold port; you will need to obtain an appropriately sized, threaded plug to do this. Plug the open EGR tube and/or pinch off the vacuum hoses(s) that controls the EGR valve. What you're doing here is making sure that nothing other than gasoline-air mixture can enter the Carb or manifold for intake into the combustion chambers. Now go test drive again and see if that stops the bucking during deceleration. Drive enough miles to clear out any spark plug fouling and residual oil that might be in the fuel system.

...oil enters the cylinders with the fuel ...

I don't notice my oil level decreasing (I usually check it everyday) so that might not be it. I'll see if I can find a vacuum gauge here. However, even if I did, I don't know how much is normal.

Regarding the spark plug cables test, I watched my mechanic do that. There's no difference in the reaction between cylinders.

Been there! Done that! Had similar problems! Couldn't tell that the mount was broken until I had someone else race the motor while I was looking under the hood. Sudden engine torque cause engine to rock more than it should, causing issues with the carb. linkage. Replaced broken motor mount and problem no longer existed. Maybe vulcan needs to spend his money following the advice of Gurus. After all the rest of us don't seem to know much!

TMF

Hey TMF, I didn't say you couldn't be right. I just didn't see the connection between a loose or missing mount and my problem. Besides, being a Guru doesn't guarantee anything (I'm a Guru too).

Just to inform you, I found a mount that's missing a bolt! I don't have one on hand so I'm getting one tomorrow. I'll come back and tell you guys what happens.

Regards,

Vulcan

Years back I worked in a Chevrolet dealership in Brooklyn. There was a long running problem with motor mounts with Chevys. The driver's side motor mount would break. When you stepped on the gas pedal hard enough, the engine would lift and hold the throttle open. Kind of like a wide open throttle cruise control. The throttle would stay pinned to the floor till the power was interrupted the key, or the power fell off from over revving the engine. The government eventually made them issue a recall that went back to the mid sixties. This was in 1974. The repair was braided steel cables that would limit the travel with a broken motor mount. We did lots of motor mount cable installations.

Back in the early sixties I owned several different Chevy's of various years. I raced some of them. My dirt tracker was a stock Chevy powered 340 hp/327 ci ordered direct and delivered complete on a crate. I re jetted it for use of methanol, and won my share of races.

You are very correct about the motor mounts breaking, When ever I suspected a loose engine as a problem, the MM's were the first place to look. It is a no cost inspection, and this was why I suggected thet Vulcan look here first.

I have a small ranchette with some livestock on it that needs to be feed nightly. I don't live there, so I drive a 4x4 Jeep Cherokee there daily. It shows that I have 266,000 miles on the engine and drive train. The only care it gets is regular oil checks and fluid checks and a Walmart battery every 2 years, unless something else breaks. I always look for the cheap fixes first, and eliminate them as I go until I find the problem part. SAVES A LOT OF MONEY, TAKES A LITTLE TIME. Some times it even works out as preventive maintenance.

Modern cars have front wheel drive and many of them only have three MM's. 2 by the fire wall and only one in front of the engine. I find the single MM' most likely to break, and easiest to fix, and the one that could likely be the cause of Vulcans problem. He mentioned that he checked and found a bolt missing there. I hope he doesn't have to look and further. If he does, he will likely be paying a mechanic to correct this problem.

TMF

I am hoping to allow Vulcan to be able to go to his friendly mechanic, and have a reasonably good idea what is wrong with his car. The list that he had this morning would pay for the mechanic's son's first year of collage. I would just like to give Vulcan a fair shot there.

The list...would pay for the mechanic's son's first year of collage

You're so right.

I'll have to tackle this one by one though. I'm having the clutch fixed first. It seems to be the most likely suspect.

I had my neighbor try driving my car and he remarked that my clutch seems a little deep (translated from the native language). He means that he just needed to lift his foot a little before the clutch reengaged which shouldn't be (according to him).

Assuming that doesn't solve the problem, I'll try having the carb taken out and cleaned.

I think it's best to do this one at a time just to be able to identify the root cause. If I have everything done one time, aside from being expensive, I'll never know what was causing it. I think we'll all want to know.

By the way, I replaced the bolt on the motor mount (well, not me exactly) but nothing changed. One down.

"I'll have to tackle this one by one though. I'm having the clutch fixed first. It seems to be the most likely suspect.

I had my neighbor try driving my car and he remarked that my clutch seems a little deep (translated from the native language). He means that he just needed to lift his foot a little before the clutch reengaged which shouldn't be (according to him)."

If your car is jerking on deceleration, without your foot on the clutch, the clutch would have to be slipping to cause this. If the clutch is engaging too close to the floor, that is not the signs of a slipping clutch. Slipping clutches usually grab close to the top. If you can not find any other reason to replace the clutch other than the grab location being low, save your money.

Hate to rain on your parade, but just because the bolt was replaced, it doesn't mean the mount is still good. In fact, it implies that the mount may have been overloaded at some point. Modern engine mounts are more complicated than most people realize. Here is a link to a basic description of the mounts and how to check and replace them:

http://www.popularmechanics.com/how_to_central/automotive/1272286.html

[ Note: If typing the link, it should be ".../how_to_central/...", i.e., underscores not spaces ]

I'd also suggest you make sure the advice you receive is applicable to your vehicle. Some vehicle builds are region or country specific. For example, in 1995 the 1.3L engine was not an option for U.S. sales (they had 1.6Ls). I'm not saying there's going to be any practical difference, just to be aware that there may be. In this example, the displacement difference could mean a different engine or simply a change in bore and/or stroke. The former could result in different mounts and locations while the latter would have no impact (I don't know what the actual differences are, I'm just speculating here).

Best of luck,

-eef

You are absolutely correct sir/maam, The missing bolt may only be the tip of the iceburg with the engine mounts. Who knows... there could have been other parts falling off on the road right along with the bolt, like say some washers, gromets. and not to mention, if the car has been driving without the bolt, causing the engine to constantly slam on the mount, its bound to be worn anyway. (I would deffinately be looking closely at ALL the engine mounts, and deffinately be contimplating (seriously) about replacing them.

Vulcan,

Now you know why, except for very narrow and specifically identified problems, you don't come to CR4 with car problems.

Everybody's a GURU!

Seems as though you have as many answers as there are parts on that simple little car. Most of them, although I have been driving and working on my cars for over fifty years, I have never seen on any car although as concepts not impossible and some so esoteric as to be pure fantasy.

Best advice for today outside of finding a very competent mechanic which I gather you have not; just continue to drive it and sooner or later whatever is causing your problem will get so bad as to clearly manifest.

But writing this there is one thing I don't remember anybody mentioning. If that car has a little electronic package that switches the spark coil (Trace the primary spark coil wire back and you might find a little 2x3 inch block screwed to the firewall or wheel well), change it. It's cheap, about ten dollars, and speaking empirically, I have seen, on two or three occasions, that item associated with the problems you report, but usually on a Dodge or Chrysler product.

Nonetheless, like I say, everybody here, is a GURU!

j.

Watch what you say. Gurudom is about to come upon you. But you'll need to give up using first.

That part your are referring to is the ballast resister. It was used on all of the domestic Chrysler products from the start of the electronic ignition era, till the Lean burn vehicles. And yes you are right. Any Chrysler product that did not run correctly needed a new one. And every person that was doing road service calls carried a new one with him, because it was easier than towing. And jumping with a paper clip generated no repairs.

Jack, Bob,

Assuming your are both referring to the same thing, it has evidently been forgotten (after all these years) that the only symptom of failed ballast resistor is (or, rather, was) engine dying (typically at idle) momentarily after startup...never under load or anti-load (as result of high vac) while driving...because the engine stalls before the vehicle can be driven (more than a very short distance, if at all). The sole symptom and failure mode of ballast resistor fault was not unique to Chrysler-made vehicles. It was always a tricky failure mode (the first time) because it generally presented just after ignition tune-up renewal (ballast resistor change not being routine a part of that procedure).

Hi Jack,

I don't mind the volume of advice. I learned a lot of things and, for that, I have you and the others to thank.

You're right, I need to find a competent mechanic. Preferrably, someone who's worked in a Nissan service center perhaps.

Regarding the electronic package, I'll have a look though I've gone over the engine several times now and didn't find anything electronic (ignoring the starter, and other electrical things. I don't consider them electronic).

I don't think everyone's contribution was because they "know" what's wrong. With the amount of information I gave, it's probably not enough to give a 100% sure diagnosis. The guys are being helpful and giving what they think may be the cause of the problem. That's the essence of the Guru, in my opinion.

Regards,

Vulcan

I've seen worn clutch / weak pressure plate exhibit this kind of symptom. Sudden and hard deceleration actually causing the clutch to slip and grab which gives the jerking motion. If this is the problem it usually won't be long before sudden and hard acceleration starts giving some slip.

Clutch eh?

I have noticed that shifting to first gear is sometimes difficult. From full stop, I depress the clutch and shift to first. Oftentimes, I have to gently coax it before it goes in. If I try to push too hard, I get a "click" when it engages which I'm sure isn't normal. Would that be a symptom of a clutch going bad?

oh yeah - and a second thought here, when it doesnt want to go into gear - try releasing the clutch just a tiny bit to get it into gear, if that works... and it goes right into gear, your clutch is worn - if it doesnt help...

then your shift forks are worn out - but shift forks wont cause jerking motion

...try releasing the clutch just a tiny bit to get it into gear...

Dang! That worked! When shifting into gear, I tried releasing the clutch a bit and it went in smoothly.

Okay, this is starting to sound like a clutch problem. I'll have it replaced soon as I get my 13th month bonus (there goes the new LCD monitor I was planning to buy ).

but before tearing down a clutch that may or may not need it—driven by one who knows how, a stick shift should not need clutch work within the normal life of the vehicle (how many miles again?)—you should check clutch free play (at the pedal) and adjust as necessary. If it's got hydraulic clutch, assure that the fluid level in clutch fluid reservoir is not too high...or way low. Reserve fluid level could be a "tell" indicating excessive clutch wear; or defective slave cylinder return spring. Again, these are unlikely faults unless the vehicle has "ancient" mileage; or has been driven by one unskilled in manual shift operation...and increasingly likely prospect these days....however, the "normal" indication of improper clutch usage is clutch slippage, not clutch grabbing. If the vehicle has less than 100K, there is some likelihood that the manufacturer will share in repair cost (in the USA) if teardown is required.

I have no idea what kind of clutch it is. I always thought that all clutches were the same except for size, I guess.

I don't know how to check the fluid level. I don't see anything like a dipstick or I just don't know what it looks like. I only know about the engine oil dipstick.

It's got about 131,000kms (<82,000 miles) on it.

Drive it to Florida, and I'll check it for you.

Or, look next to the brake master cylinder for another smaller reservoir that could hold only about 4 oz. of fluid. It should be in line with the clutch pedal.

Drive it to Florida, and I'll check it for you.

Well, that would really hurt the old wallet! 'Wonder how much it would cost to ship it to the U.S. (including my plane fare)? I can imagine the U.S. embassy official looking at me as I apply for a visa.

"You want to visit the States to see who?! To do what?!"

Thanks anyway. I'll check for that reservoir.

regards,

Vulcan

If you only had an ocean going car...maybe a mast and sail..then just run before the trade winds (up the china coast, across to the west coast, then through the Panama canal and your almost to Florida. Starting now's about the right time to catch those westerlies to Califorinia.

When you push the clutch pdeal you are either pulling on a cable (directly or via a lever), or pushing on the piston of a cylinder (again, directly or by a lever). With a cable actuated clutch (release or "throwout" bearing, pushing the clutch pedal causes the cable to pull against a kind of finger at the side of the clutch housing which forces and disengages the clutch. With hydraulic clutch, applying clutch pedel pressure applies hydraulic pressure at a slave cylinder located coaxially on the output shaft into the transmission. This forces the clutch plates to disengage in the same way as the cable, only pressure is applied straight along the clutch center and not from the side.

You can think of either clutch type in much the same way as mechanical or hydraulic brakes. Tension on one end of a cable forces an action (such as applying brakes) on the other end; or "compressing" fluid in a master cylinder causes piston movement (via hydraulic tubing) at a "slave" cylinder to actuate a brake. You should be able to quickly tell which kind of clutch by looking behind the clutch pedal.

The clutch fluid reservoir, if you have one, is typically mounted inside the engine compartment on the firewall in front of the driver.

Remember that if the clutches are worn down, the fluid will be too high in the reservoir (hydraulic clutches are funny that way). If the fluid is too low, its and indication you are losing fluid via a leak somewhere. I reiterate, that clutch grabbing is not typically a symptom of overworn clutch surfaces; that will show up a slippage when you try to accelerate the car from standing position and at gear changes...excessive fuel consumption as well.

Finally, noting you island location...I'm led to ask whether the car has been exposed to salt spray or water near the ocean or China Sea? If so, it is then possible that corrosion has damaged clutch components and linkages which could in fact cause grabbing. One way to judge would be to look under the car for excessive corrosion of the under carriage, drivelines, housings, wheels, etc. If these are badly corroded, it's reasonable to surmise that corrosion has also occured inside the clutch housing.

Finally, you would be wise to try to obtain the owner and/or maintenance manual that originally came with your vehicle...it will help you become more familiar with your car and engine systems. Searching the internet will be a good place to look.

Okay, my car uses a cable and there's no reservoir other than the brake fluid. Regarding corrosion, it's an old car and I must confess that the body needs some work on the underside of the right rear door. Other than that, I can't see any other corrosion anywhere.

I live about three kilometers from the sea (straight line) and travel to/from work on a "coastal road" (which is about 200 to 500 meters from the sea) and my place of work is about a kilometer from the water's edge.

Regarding the owner's and/or maintenance manual, I tried getting one on the internet but no luck. The guy I bought the car from lost his copy. I tried asking around but no one's either willing to give their copy or sell it to me. The Nissan service center here will sell it to me but is asking for the moon.

Okay...so your clutch release bearing actuation is mechanical. Good work there checking it. Now, by free play I mean that when you push the clutch pedal with you hand, it will move a very short distance (about a pinky's width, more or less) before tension is placed on the cable. In other words, when you clutch while driving, the pedal will move a very short distance before and tension is applied to the clutch cable; the reason is so that when the clutch pedal is released and clutch is engaged, the clutch will remain fully engaged and not be (ever so slightly) disengaging due to tension on the cable when there should be slack in the cable. Miss-adjustment of clutch cable free play can lead to wear and clutch performance symptoms and hastened wear and tear.

At this point, I believe you best course is to abandon the clutch cause for the time being...because, as I've told you in another post, there's good reason to believe your problem is with poor oil control in the engine. You should endeavor to verify or eliminate oil control problems (related to normal or abnormal vacuum)...after which, we can come back to the clutch thing...but I doubt we will need to.

...also symptoms of normally performing clutch/gears.

The click and the hard shifting would be indicative of a failing throw-out (realease) bearing or impeded bearing actuation. But, recommend you check the clutch cable along its entire path and look for places of binding or unfree movement. Some trannies have a cover plate over a port through which the bearing can be viewed. Typically on the right side of the clutch housing.

I have seen issues where asst. linkages attached to drive train functions that performed incorrectly because the MM's, one or more failed. I have seen engines actually become locked into a situation in which the engine over revved and demolished connecting rods and and crankshafts because the carb. linkage became jammed as the result of the rotation of the unrestrained block attempting to turnover where it was formerly anchored.

This does not mean that a broken motor mount is the problem but it is very inexpensive to check this out first. I have a 1988, 2000cc Oldsmobile Firenza, that has been in storage for a few years, engine and trans. and other parts intended for use in a hho only powered custom car. It suffered similar studdering problems, so I had my wife race the engine while I peered beneath the hood. "YOU COULD HAVE GUESSED!" Broken front motor mount.

TMF

Manual or automatic transmission?

It's a 5-speed manual.

To rule out the brakes, when the car is cold, and has been sitting for a few hours try this. Drive the car in a manner that will cause the car to "jerk" as much as possible in a short distance, Give yourself plenty of room, and try to stop only with the parking-emergency brakes. Once you come to a stop, test the front wheels for heat. If you only stopped with the parking-emergency brakes, there should be no heat at the front wheels.

My guess is that the throttle bypass valve system is not functioning correctly. This system is used on emission cars to prevent high vacuum conditions from sucking raw fuel through the carburetor. When slowing down, the throttle is closed, creating high vacuum conditions at the idle passages, drawing more fuel than it would if vacuum were at a more normal condition. to solve this, engine manufactures use a throttle bypass valve to allow the high engine vacuum to be released to the other side of the throttle body, avoiding the over fueling when decelerating. The valve is signaled by the engine's computer. It senses engine vacuum, engine speed,and throttle position.

Now for my guess. Your throttle position sensor is out of adjustment, or defective. Or your throttle return spring is not strong enough to ring the throttle position sensor all the way back to the idle position, unless you snap it back. On an American sold car, the condition you describe should trip the "check engine light" I do not know what equipment is on your car, so I am not sure how to tell you how to check for the problem. A start would be to remove the air cleaner, and crack the throttle open enough to bring the engine above about 2500 rpm, then release. If you hear a louder vacuum type noise for a second or two as the engine slows down, that would be the throttle bypass valve in action. From the location of the sound, try spraying a carburetor cleaner into the carburetor air inlet and repeating the throttle cracking procedure. If the valve is just gummed up, and sticking, this should cure it if you get the cleaner in the right spot. Try that, and let me know. good luck.

Okay, I understand your proposed test for the brakes. If the brakes are engaging intermittently, the front wheels should heat up as I drive. I'll check that tomorrow (it's 7:30pm now).

About the throttle bypass valve, my car doesn't have a computer except for me (which probably explains why it's been having these problems ). Would a carburetored engine have a throttle bypass?

I tried spraying a carb cleaner into the carb once. Scared the hell out of me. The car made like it was choking to death! I never did it again. Leave the job to the experts, right?

The mid seventies Chrysler products were not computer equipped, and had a small metal encased circuit board with only 3 wires on it for this function. One to the ignition switch, one to the electronic ignition control module, and one wire to the vacuum solenoid that had hoses attached to each side of the throttle plate. Try looking for this device on your car. A service manual would be very helpful at this point. Try looking for any device attached to the carb that might serve this function. If you find a possible suspect, disconnect the wires on it, and retry it.

As for the spray carb cleaner causing the engine to sound like it was going to choke to death. What did you think would happen when you sent the engine twice the fuel it needed to run on? Spray it in short blasts, wait a few seconds for the mixture to regain normalcy, and shoot again. As a guess, try 33% spray time, and 67% wait time. Short sprays.

The only way to clean a carb is to completely dismantle it, clean all the parts in suitable solvent and reassemble it, (taking care to lose a few small springs in the process.)

Spraking it doesn't constitute 'cleaning it'.

Del

Once again I have neglected to make myself clear. The throttle bypass , if built into the carb would be exposed to air flow directly from the air inlet area of the carb, and would receive the spray pattern from the spray can. The spraying procedure should be used as a test to determine if it changes the jerking. If it changes the jerking, thorough dismantling and cleaning would be required, of course.

so true, so true...

Throttle bypass with carburetor? No.

Late seventies Chrysler rear wheel drive vehicles called the system the converter overheat protection system. The throttle was held open whenever the engine was above 2000 rpm. Open throttle speed was controlled with a throttle solenoid, similar to the solenoids used to control engine speed when the ignition switch was turned on, or an air conditioning speed increasing solenoid.

The measured gap between throttle plate and throttle body in a carburetor serves the purpose of throttle bypass. However, a carbuteted system is not deemed to have a throttle bypass (circuit) in the same sense as a fuel-injected system.

Hope this clear up that issue.

You say:

The brakes have been replaced; the carburetor has been cleaned; the distributor adjusted (eventually replaced when it developed a leak); fuel filter replaced as per schedule.

Do you mean:

1. That the problem first appeared after (even though) those things had already (presumably recently) been done? Or,
2. That doing those things did not succeed in fixing the "jerking" problem?

Since you have a carbureted engine, a vacuum guage will not be expensive: probably about $10, give or take. I would recommend performing vacuum check both underhood (in accordance with gauge instruction, while driving the car, trying to reproduce the fault. Check for abnormal vacuum reading that will indentify or narrow the problem. Let us know what you come up with.

Hi Vulcan, "kabayan" (local word for same nationality). That sort of thing always happen to me, acceleration and decceleration (without using brakes) in my kia pride 1.1 carburated engine. I think it goes with carburated low displacement engines. I usually avoid this by pressing on the gas pedal once again but lightly.

...it goes with carburated low displacement engines...

It does? I'll have to ask around to confirm that but somehow I'm not willing to accept that. Besides, I've had the opportunity to drive a 1.3L, brand new, car and it doesn't do the jerking thing. 'Course it wasn't a Nissan (Honda, actually).

Is it your opinion that this car, when new and being driven with a car sales person, would buck, and jerk like the OP describes? This would make it very hard to sell these cars.

sounds like clutch/drive line issue to me - if the engine mounts check out okay and if it's not a worn clutch, the gears in the trasmission could have too much back lash (worn out), or worn out u-joint (or cv axle as the case may be) - is there any noise associated with this? if there's a loud clunk when you move from forward to reverse gear, that would point to the ujoints/cvaxle...

either that or there's a worn out spring or something on your choke causing it to close and open freely as the engine builds and looses vacuum

i like the last comment there - if it only happens when you stab the throttle or let it go suddenly... don't do it?

Another way to check for it being related to the engine/trasmission would be to clutch as soon as you let off the accelerator, if it still jerks, then you know it's not engine or transmission related... that would eliminate a few things

dont touch your brakes/wheel hubs after youve been driving. they do get warm/hot just from regular use... it would be abnormal though if they were glowing red hot... then you'd have a serious problem (unless you were racing pikes peak)

i like the clutch and my transmission guesses the best so far... perhaps take it to more than one mechanic and get some professional opinions :p

is there any noise associated with this?

No, no noise.

when you stab the throttle or let it go suddenly... don't do it?

Only when I let go. I try to avoid releasing the gas too quickly but I can't do it all the time. Besides, I have to let it off veerrryyy slowly to avoid the jerking. I've had to drive very carefully and slow down from waaaay back before coming to a traffic light or similar.

...clutch as soon as you let off the accelerator...

That's what I do. The jerking stops when I step on the clutch.

With regards to the brakes, the front wheel hubs were warm after driving a couple of kilometers though I avoided letting it jerk continuously. The jerking gets very severe if I let it continue. Curiously, the severity seemed to reduce after about 5 seconds but it didn't go away completely.

Hello Vulcan,

I had a very similar experience the cause was a broken camshaft; go figure...

Hi Vulcan,

I had a Datsun that jerked that way before. I believe it was ignition problems, but it was along time ago. Have the ignition system checked out.

S

We did have a Nissan for about 13 years in Switzerland. It was one of the last models with normal carburator. We noticed the jerking problem as well but mostly during fast acceleration in the 1st and 2nd gear. While decelerating it was jerking too but much less intensive. Our mechanic told us that the Japanese fuel specification for 95 octane is actually not like ours in Europe and that we should better fill in 98 octane to get rid of the, as he called it "lean fuel jerks". We tried 98 octane, it worked fine w/o jerking but finally we fuelled the car with the cheap 95 crap only and avoided to drive the car in just that conditions when the jerking would occur. The engine was always in very good condition through all the 240'000 km that this Sunny took us around.

Hmm, I don't know. The recommended fuel is unleaded which is 95 here. I'll have a test and fill up with 98. Not now though. I just filled it up the other day and I haven't used the car much. The needle on the fuel gauge is still above the max line.

Actually, if it wasn't for the jerking, the car's fine. It's got 131,000+ km on it and it never stranded me on the road (except once when I ran over something and burst my left rear tire).

kabayang Vulcan....hello I have similar problem with my toyota corolla 1990 carburated engine it also jerk when I lift my foot on the pedal...by this forum I learned that it may be...the clutch since sometimes during uphill if I press too hard on the accelerator pedal the clucth slipped and rev up high...I agree with one comment that during removal of your foot on the pedal try to push the clutch and check if it is still jerking..if not then not clutch problem and go to engine mount and ignition timing..check your ignition belt for sign of worn out or chirped out or loose pulley tension...please update me as well as I will update you for any improvement on my car...

thanks...

r.zamora

Hi r.zamora,

Yes, the jerking goes away when I step on the clutch. I get my 13th month in a couple of weeks. Guess where it's going to be spent?

regards,

Vulcan

Vulcan,

I did mention clutch back there a way but it will cost you something like two hundred U.S. dollars to replace a clutch that you don't yet know is the problem.

Think about it. It stops jerking when you release (Step on) the clutch. If the engine is jerking for any reason whatsoever car would stop jerking when disengaging the drive train from the engine by clutching.

Problem is this is the sort of thing that looks like too many things.

Nonetheless, you seem to have had some work done on the distributor. Bad point adjustment would cause your symptoms. It costs nothing to check that point adjustment. Point adjustment on small four cylinder engines is critical.

Seems like some mechanics are making out on you from some of the stuff you mention. My experience is 99 out of a 100 don't know their ass from their elbow and I am a fair mechanic. And, unless you are rich and don't care, you need to know that you sound like the classic sucker. Before you get mad understand you need to hear that.

Seems like you need to become mechanic enough so as not to get screwed. Some of the stuff you are being fed here is pure garbage. Get a good repair book on that car and start reading.

Changing clutch disk and pressure plate is a last move. It is expensive. And, if and when you do, the throwout bearing of negligible cost, should be changed too insofar as the labor is the same and most of the cost.

Odds are, from what I read here, is that the culprit is a simple point adjustment.

Engine can be checked generally if you know a mechanic that has a Sun Machine and knows how to use it. That would separate all possible engine problems from drive train, etc. It is remote that it could be a brake problem.

My own opinion is that folks should not be allowed to own or operate a car save they know and understand their workings.

Get the mechanics book for that specific car. Get a book that goes through car systems as a general overview and get to understand them. Then you have the tools to do real material analysis based on observed data instead of the hodgepodge you are getting here.

Given all that, unless you work on them all the time as a paid mechanic, it is still possible to make mistakes but much less so when you know and understand automotive systems and the particular car. Indeed, I made one the other day based not on lack of general knowledge, but rather the specifics of the particular car. Because I didn't know the car I should have had it checked by a demonstrated competent mechanic I sometimes use. Because a friend was involved I didn't.

Nonetheless, if you drive one you need to know and understand it. That may also mean you need to get some background in basic principles of electricity and hydraulics as well. It is, after all, in the books and on the net.

j.

...had some work done on the distributor

It was replaced. There was oil leaking into it (I personally saw that).

...need to know that you sound like the classic sucker

I can understand that. When you know very little, that can happen.

Get a good repair book on that car

'Tried that. Tried the 'net as well as asking people (even those I don't know) if they can sell me their manuals. A Nissan shop was willing to sell one to me but was asking for the moon.

My own opinion is that folks should not be allowed to own or operate a car save they know and understand their workings.

I would not make such a sweeping statement since not all of us are mechanics and it would be unfair if only mechanics are allowed to drive. I studied cars and engines with whatever materials and time that I have. I have most of the basics down pat but something like diagnosing a car problem may be difficult.

Still and all, this thread has been very informative for me. I'd still thank you and everyone else for all the information. If ever I get the problem fixed, I'll come back to say what it was.

All in the spirit of CR4.

regards,

Vulcan

"If ever I get the problem fixed, I'll come back to say what it was."

No you won't. None of these problems ever get solved, and then posted.

You don't need to be an auto mechanic to drive a car. And any fool can change parts. You already have what you need to fix this car, logic, and common sense. Just go slow, and if you can't understand why something is happening, ask.

I do not know type of vehicle a LEC is. That model is not sold in the US under that name. Can you describe it more, or can someone more familiar with that model translate for me. I do not see anything but clutch cables listed for most of the Nissan products sold here in 95. That is good, because cabels have adjustments on them to allow the grab piont to be moved.

None of these problems ever get solved, and then posted

However long it takes. I'll post if it gets fixed. By fixed, I mean that the problem goes away. If it goes away then comes back, that's another matter. That would be a parts quality issue, an installation issue, or a driver issue .

The Nissan LEC is similar to the Sentra. In fact, they look the same on the outside. Unfortunately, I can't find anything about the '95 model in the 'net so it's probably only for the Philippines. Last night, I was able to get a pdf version of the '96 model of a Sentra (1.6 liter engine) except that it's got a computer and direct injection. It looks very similar except for the absence of the carb. The quality of the print is not very good, unfortunately, so the drawings are not very clear.

When I searched the Nissan offerings here in 1995, I found that the Sentra has a clutch cable, so you should be able to rule out a hydraulic clutch linkage problem.

1 down, 200 to go. The wiring diagrams of the engine will not help too much if the emission equipment is not the same. I will try to find the last carborated Nissan I can.

If you throttle down, and the car starts to jerk, you can step on the gas, and it will stop. Correct? If you now back off the throttle gently it will be gone still?

search for Nissan GA 1.3L edition

What is a Nissan Good Answer?

Oops! GA series is pertinent nomenclature

I did search for Nissan Good Answer... err... GA13 series. Nothing comes up. 'Seems I have the only car of this series.

Follow this link

Thanks but I followed that months ago. The 1.3L version doesn't seem to be popular. Thanks anyway.

...will be gone still?

The jerking stops when I reapply the gas. If I back off on the gas slowly (believe me, "slowly" is very slow) the jerking doesn't happen. At least until the speed drops too low which tells me that I need to change gears.

Talk about whistling through the grave yard! How many ways are there to fix what seems to be a throttle plate out of adjustment.

Eight or nine come to mind without thinking hard...Depends upon which ever way it's loose, deformed, cracked or which contributing component may have any of the fore mentioned and/or additional malfunction.

It is a consideration and nice of you to point it out.

Check the inboard cv joints. Outboard cv joints make a knocking sound when you corner, inboards give a jerking sensation when you let off the gas.

CV joints, right.

_{(add another thing for the mechanics to check)}

Check the throttle plates
Clean the carb
Check the brakes
Check the clutch
Check the CV joints

Gawd!!

WAIT! Don't forget to have the valve caps checked.

If, the clutch was the problem, what would taking your foot off of the throttle gently do to change how it acts?

If the problem is a throttle bypass device that is not functioning properly, releasing the clutch would allow the engine speed to drop to idle speed, and switch off the throttle bypass device, and stop the jerking action.

Do you have a tachometer on the vehicle? Watch the tach when the jerking is happening. If the tach is jumping, the problem is engine related. If the tach is steady, the problem is driveline related. If your car does not have a tach, I would suggest trying to borrowing one to evaluate with.

Hmm, good point. Seems my mechanic's got more things to check now.

No tacho, unfortunately. Further, my mechanic broke his just recently. Engine's hum (once it's warmed up) is steady. In the mornings, the note changes every few seconds or so but this goes away after several minutes.

Vulcan, trying to diagnose the problem without actually being present is difficult, which is why you should hold off on part swapping until you nail down the problem. Before getting into engineering, I went to auto serviceing and diagnoses classes, worked as a legitimate mechanic, rebuilt several engines, and worked at a tranny shop as an R&R guy to pay the bills while going to school.

You can skip looking at differentials or U joints, becasue front wheel drive vehicles do not have them and judging from the year and size of your engine, I'd guess your vehicle is front wheel drive. The most common problem I ran across that fits the description you initially gave would be the inboard Constant Velocity joints. One quick tell tale sign that you can check for yourself is to simply look under your car and check for cracked or missing rubber boots on the ends of your axles. The obvious ones are the outboards near the wheels. When you locate those, follow the drive shaft from your wheel to the tranny and locate the rubber boots near the tranny (inboard CV joints). If the boots on the inboard CV's are damaged or missing, it's pretty much a no brainer that the joint or joints are bad. The outboard boots are more exposed and a cracked outboard boot means you need to replace the boot before the joint goes bad, but the inboard boots are reasonably protected so if it's damaged, the joint is usually bad. If the inboard boot is intact, it still may be bad, but now you have to get someone who knows to take a ride with you. A good mechanic will be able to tell you immediately if the joint is bad without tearing anything apart.

You will need a flashlight, but you don't have to pay a mechanic to do a basic check. Check it out before you start dumping money into parts or messing with the fuel system.

I'd guess your vehicle is front wheel drive...

That is correct.

look under your car...

I've have a look but I'm not sure if I'll be able to tell unless it's badly worn or missing. Won't hurt to look though. Thanks.

Check the fuel filter...

I've read posts through #33........

Lots of experience posted...answer gotta be there some where...or in combination of responses.

Two points:

Small displacement engines can make up for torq with rpm/gearing.....except in compression braking....

Still, I would concur it is a vacuum related problem

One thing not mentioned is bad U joints/worn drive line splines which can produce similar experiences...but usually not as "violent" as I sense from your original post.

MR. GUY

It is called compression braking

95 Nissan with carb. and standard trans . Right ?

Ok ., firstly , there is a good possibilty that the carb is a " computer controlled carb ".

These were introduced before actual computerised fuel injection systems were adopted and are a nightmare to try to diagnose . Does the carb. have a lot of wires connected to it ? If not you can diagnose the carb. as usual , which brings us to the carbs. dashpot . This small cheap externally mounted to the carb. vacume operated device prevents the throttle from snapping shut and sending you through the windshield when you come off the gas peddle quickly. It could simply have a leak in the diaphram and is now intermittant and causing the jerking . This is a cheap enough part to replace first and test drive later. To test this part you must go to a suitable manual or website to identify it and vacume test it for proper operation . Clymer or Haynes manuals for you car are about $ 15.00 at any parts place . For web help go to All Data. com . I suggest you get one or the other as i assume you are trying to fix it yourself .

Keep me informed if any of this helped .

...trying to fix it yourself

Good heavens, No!!

I just want to get a few (well, got more than a few now ) hints about what might be causing it.

I've checked the 'net for a manual (previous owner lost it) but only found one for a different engined model (1.6L) and it was computer controlled direct injection. Mine's a carburetted 1.3L. No computers anywhere.