94 Chevy Blazer Driving Issues

Hi Tiredofcarproblems,

Welcome. Here's the thing. The more you tell us the more we help you.

When?

Is it consistent?

Hot or cold?

Does it start easily.

Give us a couple of short paragraphs explaining the symptoms, etc..

It starts easily when first started,it idles fine but hesitates when hot and cold the longer i drive the more it hesitates and wants to stall.It is consistent,it happens more after the first 15-20 minutes of driving then when you first start driving.It has new plugs,the wires seem good,using mid-grade gas with fuel injector cleaner added to each tank,and sometimes if you drive for a little bit then stop go into the store come back out and start it up it will run fine.

Also the engine only has 40,000 miles on it

At 40,000 there are some things that come to mind. If the engine wants to die out when the throttle is hit, I would think that the engine is leaning out, or the spark energy is not sufficient to light the suddenly lean mixture.

I believe 94 still has a distributer rotor. Pick up the cap, and examine the rotor for signs that the spark is jumping through it to ground at the distributer shaft. At 40g, you should probably just buy a new one, and change it. Under $10.

If this looks good, or does not solve the problem, look for electrical burn marks around the ignition coil. The last of the GM coils were prone for this. You might be able to see the spark jumping at the coil at night. With a cold engine, open the hood and turn on the ac, and look for the arcs around the coil. ( keep the area as dark as possible)

The hardest of the possible cures is to replace the gas filter. A restrictive fuel filter can lead to low fuel pressure, especially when additional power is requested by hitting the throttle. Under normal conditions, the fuel injection system will sense the power request by means of a drop in engine vacuum. Under those conditions, the fuel pressure regulator would raise the fuel pressure. But if your fuel flow is restricted, the pressure would not be able to increase when needed. It is possible that your fuel pressure regulator is malfunctioning, but you would need a fuel pressure tester to determine this. Do you have access to a fuel pressure gauge? Good luck.

What type of engine?

I will point out that GM had a problem during this time with EGR valves hanging open during operation on certain V6 engines, including some of those installed in these vehicles. Carbon buildup/intrusion in the valve would cause them to hang open, causing severe driveability problems. Just a thought.

You may check ignition coil , which may malfunction when it is somewhat hot , after driving some distance , and also change condenser in the distributor .

If it was me, i'd burn it, take the insurance money, and buy a Dodge.

Would that be the heated rear glass model to keep your hands warm while pushing?

Check the fuel system. It probably has an electric fuel pump in the fuel tank. Sounds like the fuel pump may be going out or you have intermittent fuel pressure drop due to a restriction in the fuel filter or fuel hoses breaking down. The fuel pump relay maybe developing excessive resistance and may be about to fail.

Does the check engine light come on? Have you checked for any codes on the engine control computer? Could be a defective or out of tolerance sensor. If the engine has less than 50,000 original miles the emission system may still be under warranty.

As mentioned above, my vote is on the fuel pump.

I've had several electronic fuel pumps (the ones inside the gas tank) die with similar symptoms. As the pump wears out, it tends to get "louder". IMHO this is a good sign that you should have your fuel flow & pressure (BOTH) tested or just replace the pump.

It will begin to intermittently fail to provide adequate fuel flow/pressure for driving, but will be fine under starting and idle conditions. During normal driving and acceleration, you'll get sporadic hesitation and the occasional complete stall. A STRESSFUL event when it happens in rush-hour highway traffic! Been there, done that, not fun.

Good luck!

We generally start with the simple / easiest to do things first. To change or have it changed, the fuel filter can very well be your vehicle's problem. If you don't know the safe and correct procedure to change the fuel filter , please have a qualified mechanic do it for you. There is pressure in the fuel line that you must relieve before attempting to remove the filter. When the filter is removed we just drain it opposite of the way the fuel is pumped in and if there is any rust, dirt or water in it , it will usually run out. This is the first , simplest and cheapest route to go. If the filter doesn't solve your problem then you might follow some of the other suggestions offered.

Thank You all for your help and suggestions,I think it may be the fuel filter which i have bought and plan on replacing,if that doesnt work i will definately try the fuel pump..once again thank you all it is appreciated!

This happened to me, different vehicle, same symptoms. It is a fuel problem, many years of accumulating dirt or fuel contaminants in the tank. If replacing of the fuel filter does not solves the problem, disconnect the fuel line from the filter( next to the engine),drop the fuel tank, and remove the fuel line, from tank side, blow air into it to remove any debris it may have. electrical pumps are almost fails safe, but they do clog, with the tank down remove the fuel pump and inspect the pump and filter.

Drain all fuel and leave it open to remove any water, by aeration. reverse all actions and car will be running fine.

If there is multi-scan equipment available, I would like to suggest on carry out scanning for finding the error code that persist. Did you noticed 'check engine' light illuminated on the meter cluster when the problem arise? If do so, then there is failure on the injection system and transducer component.If the engine hesitates and stall while driving or in idling, the symptoms are most likely failure in air flow sensor or meter (AFM) which either the needle of the meter to measure the air density flown into the camber are jammed or the barometer sensor faulty.Its better to get the reading from the data stream if you using a multi scan device.

There was a time when some of the GM vehicles had a problem with the air flow sensor. The simple test was, while the engine is idling, tap the airflow sensor with the handle of a screwdriver. If the engine stalled or quit running , the airflow sensor was defective and needed to be replaced. Please be aware that if you go to replace the fuel filter, you must relieve the pressure in the fuel line before you start loosening the nuts to the fuel filter. There are also special o rings on the line ends that could come off if you aren't careful. Be sure to follow the correct procedure for attempting this. Gasoline is not the best thing to be playing around with especially if you have anything such as a droplite under the vehicle with you and the gasoline runs out onto the hot droplite. If you are going to attempt this, consider using a flashlight. It doesn't set up conditions for fire as easily as a droplite. If possible also consider wearing some gloves since gasoline isn't good to get on your hands or skin. Go slow and be safe.

Hello,

The 1994 Blazer or S10 Blazer had 2-two different motors. Do you have and external coil with conventional distributor or 4.3L vortex with 3 coil packs?

Did you have this problem before spark plug & wire replacement?

Did you use original equipment replacement parts. (AC Delco)?

I CAN GET MORE SPECIFIC IF I KNOW THE MOTOR TYPE.

Some Generic Spark plugs and wires have a reduced resistance and cause a HEI coil pack to fail. The truck in most cases will run fine when cold and after the coil pack warms up it will mis-fire or fail all together. This would be the third thing I would check if it had a mis-fire problem before hand.

Or the first thing I would check if it started mis-firing a few weeks after spark plug and wires were Generically replacement.

On a conventional distributor system, when you replace Spark plugs and wires you always replace the distributor cap.

Start with the Fuel Filter

I'm starting with the fuel filter only because it is cheap and requires replacement under normal 40,000 mile (PM) preventative maintenance schedule for your truck.

If your able to work on the truck yourself, check the ground wire coming from the wiring harness from the gas tank. Make sure it is correctly connected to the frame. A poor ground connection will cause this type of problem or symptom.

Removed the fuel filter, attach a hose to the line from the tank. Run the line into a small plastic gas tank through the fill tube. Turn the key on for a few seconds and turn off. If you are receiving gas the pump is ok. Remove the hose and attach to the opposite line that goes toward the engine.

Remove the gas line connection from the engine and blow air back through the line toward the tank. (Short bursts) This will assure the line is clean. Re-attach the gas line to the engine. Install new gas filter.

Turn the key on a few seconds, and then off, repeat several times to fill the new filter and line.

Start and test drive..

If you still have problems, you can obtain the fault codes stored in the ECM. Follow the instructions in a Haynes or Chilton service manual. If you have a stored code check the emission section of your manual to obtain the code description. This will help you further trouble shoot your problem.

Your original problem with rough idle or mis-fire may have been caused by the Ignition Module. It can be removed and tested in some auto parts stores. You will have to call around to find an available store.

Again these are only trouble shooting ideas and we can help more if you can provide the engine type. Let use know what you find

Best Regards,

Tim

hello tim names Johnny i have a 94 chevy s10 4dr blazer 4x4 4.3<4l60E trans wen the things about runin temp she shuts off! i cant figure it out ive put new fuel pump.filter.dist cap.rotor.ignition mod in dist.wires. n the person before me did a whole bunch off sh!t to it as well like starter n alt n plugs jus gen mantinece i guess, i can drive it mabey 5 blocks n it starts buckn n actn like it aint getn fuel then it dies n if im lucky shell fire right bak up? but otther times it wont start bak up at all jus cranks< i hav no check lights on ive tryd to pull codes n got nothin< i jus put a brand new fuel pump sending unit n fuel filter 3days ago n still doin it. wounderin if u got any info on wat to do?

makemore geusses

the engine type is 4.3 6 cylinder vortex...thank you all for your help!

Thank you in advance for the motor type information. We'll be at your disposal for any further assistance you may need.

Note: I replaced an EGR valve on a 1995 Dodge Shadow today, it would run at an idle just fine until you put it in gear and it would fall flat on its face. It now runs great after EGR replacement.

Best Regards,

Tim

As Tim has noted, and I noted earlier, EGR problems can generate these symptoms.

I would suggest doing all the obvious checks as mentioned in other posts; fuel, ignition, so forth.

If you perform these and do not resolve the problem, EGR is a documented problem on these engines. Two problems were obvious:

1) The valve's shaft would suffer carbon buildup and stick open, causing driveability issues.

2) Chunks of carbon would be caught between the valve and valve seat.

Again, check the basics. If that doesn't do it. check EGR.

Replacement valves with coatings to prevent carbon buildup, and screens to prevent carbon entry were solutions. GM battled this for some time.

STANDARDED is right, most of the time the EGR can be cleaned and used again.

To check the EGR; you bring the engine to operating temperature and removed the vacuum line and re-install the line you should be able to see the diaphram pull the shaft up. A manual vacuum pump can be used as well. Please Note that some engines have to be in gear before EGR is enabled.

If EGR is re-used I would replaced the mounting gasket with new , replace the inlet hose and make sure the connection tube on the intake is free of carbon and slug before installation.

Best Regards,

Tim

Tiredofcarproblems, I know this thread is four day old but is you still haven't solved the problem with the Blazer, here is one more point of view. I have a 93 Blazer , also with the vortec v-6 engine, and it had a very similar problem. I Did the same as you have probably done: new fuel filter, plugs, cables, rotor and coil. These helped a bit but didn't solved the problem. I then cleaned the EGR valve (contrary to an earlier input, the valve is controlled by an electric servo, not a vacuum diaphragm) it had a chunk of carbon making is stick open. The carbon came from the engine running rich. The real problem turned out to be the fuel injection distributor (spider) which is located inside the intake manifold. This thing is sort of a very fast acting fuel valve that sends pulses of fuel to the six port injectors. connected to that valve is a damper (it acts sort of like a shock absorber for the pulses inside the fuel lines). In my case this damper was leaking inside the manifold causing the engine to run rich. This also "poisoned" the oxygen sensor in the exhaust line. I got a fuel spider from the local pull-and-save and a new oxygen sensor from NAPA auto parts. Problem solved! An extra comment: You can get the special socket for the oxygen sensor from either NAPA or Harbour freight. Without that tool , you'll probably never get the silly thing out.

I will point out two cautions concerning EGR on these vehicles.

I state this based upon my experience as a GM service engineer during this time.

1) Many people termed all V6 Chevy truck engines at this time as vortec engines. This is not correct and can lead to confusion. I assume that the OP has the actual vortec engine with electronic EGR. There is another V6 offered in these vehicles that had vacuum EGR. This is not a GM (Chevy) vortec engine, but the name was often applied incorrectly. This can lead to incorrect part selection if one does not differentiate between the two engines.

2) There are Federal and California variants for these parts, both the electronic and vacuum valves.

Hello standarded,

Good points on the EGR, they do differ depending on location and some manufacturing plants used a certain emmision system at assembly.

I would like more information on the internal intake air pulse dampener (Spider), if you can add more details to Zamaron's comment. How it works, and why it is present.

Thanks,

Tim

GM's original CPI system used a single injector and the "spider web" of plastic tubing which ended in a mechanical poppet valve at each cylinder. The second version used individual electronic injectors feeding the individual tubes in the web and the poppets.

The poppets opened up at 43 psi, if I remember correctly. Naturally, with only one main injector, all the poppets were charged and injected fuel, while the 2nd design could differentiate between individual lines. ECM used speed density instead of mass airflow for system performance parameter monitoring, again if I recall correctly.

It was done to save $$$. It was problematic as the plastic tubes would crack and leak fuel, so the owner got the thrill of replacing the spider web and shelling out the long green. In retrospect, not one of the best ideas GM ever had.

Sorry if I was not clear as to what I meant by the spider. This is just a nick-name given to the fuel injector assembly that's inside the intake manifold. It is a solenoid based metering device that sends fuel out to the six intake ports via six (usually black) plastic fuel lines. By a stretch of the imagination the gizmo in the middle with six black legs kinda looks like a spider. The damper I was talking about is part of the metering device. It keeps fuel pressure pulses from traveling back through the fuel lines. You could think of it as a miniature version of the bladder tank in a water well system. In my case it sprang a leak that allowed fuel to bypass the metering and caused the engine to run very rich. Since the fuel injection metering is done inside the intake manifold there were no visible fuel leaks or smells (except for the exhaust). My engine is a true vortec but GM used this same fuel injection system on lots of different cars and trucks. An earlier post mentioned changing the fuel filter - yes yes yes - on this system a clogged filter is the number one cause of fuel pump failure and that pump is a pain to change because you have to remove the fuel tank to do it.

Hello Guys,

Hey standarded, is Zamaron talking about the fuel injector (fuel rail) and fuel pressure line regulator?

Tim

This is a picture of the "spider" used under the intake manifold on the 4.3. A pricey item to be sure. It akso makes a good scapegoat for engine problems that do not generate a large enough profit for the poor underpaid auto mechanics. Seriously though it has been leak prone.