Re: 1993 Chevy Cavalier VL 2.2

Hi Guy’s,
I am having some problems with my Cavalier and I hope that you all can help. I am fairly mechanically inclined and I do most of the repairs around here, but I can’t seem to figure out this one:

The big problem is that the car idles very rough and sometime it’s hard to start. At idle, the car acts as if it is going to stall or the engine is going to cut out. What is really puzzling is that the car launches off the line with no hesitation and it has no noticeable misfires or lack of power while in motion. I have checked the compression and all four cylinders are with in specs. I recently replaced the ignition module because it was failing. I also replaced the spark plugs and wires.

I hope that someone has had this experience and can offer some advice.

Thank in advance!
KP

from what your describing it either sounds like a cloged cat. or a cloged fuel filter. I hope its not the ecm though.


**changes are here**

Well, I just replaced the fuel filter recently and I have a extra chip that I haven’t tried for the ECU. As for the cat, I guess I could un-bolt it temporarily and see how it runs?

KP

You have an extra chip? The 93 2.2 chip is soldered in. It's reprogrammed electronically.

Having the same experience and offering advice about which parts to replace just wastes money,imo. I've been a mechanic for 15 years. I can give you a list of parts I've changed over the years. It gets expensive though, because it's probably "one of everything."

To save money you should try to get some better ideas about how it acts like it's going to stall. You might mention whether or not it's auto or manual trans. Is the rpm extremely low? Does the engine seem to fire on all 4 cylinders? Is this problem accompanied by black smoke? If it's auto trans, does it idle rough in gear, out of gear, or all the time? When it's difficult to start is there an excess fuel smell when it starts up? Is the problem worse when the engine's warm , cold, or doesn't matter? All of these clues can point to what the problem is. Guessing is, well, a guess.

-->Slow

slowolej wrote:You have an extra chip? The 93 2.2 chip is soldered in. It's reprogrammed electronically.

Having the same experience and offering advice about which parts to replace just wastes money,imo. I've been a mechanic for 15 years. I can give you a list of parts I've changed over the years. It gets expensive though, because it's probably "one of everything."

To save money you should try to get some better ideas about how it acts like it's going to stall. You might mention whether or not it's auto or manual trans. Is the rpm extremely low? Does the engine seem to fire on all 4 cylinders? Is this problem accompanied by black smoke? If it's auto trans, does it idle rough in gear, out of gear, or all the time? When it's difficult to start is there an excess fuel smell when it starts up? Is the problem worse when the engine's warm , cold, or doesn't matter? All of these clues can point to what the problem is. Guessing is, well, a guess.

-->Slow

You might mention whether or not it's auto or manual trans: It's an automatic...

Is the rpm extremely low? : No...

Does the engine seem to fire on all 4 cylinders? : Yes, but if you listen at the exhaust pipe, you hear a "huffing" or sputtering sound. I have changed just about everything in the electrical chain (ignition module, coil packs, plugs and wires, even the battery...

Is this problem accompanied by black smoke?: No, the car never has smoked. But you can smell gas once and awhile...

If it's auto trans, does it idle rough in gear, out of gear, or all the time?: All of the time...

When it's difficult to start is there an excess fuel smell when it starts up? : It is hard starting primarily when it is warm after driving. As for after it starts, the answer is yes. I should mention also that the #2 cylinder seems to be showing on the spark plug that this cylinder is running rich. It’s very black and smells of fuel...

Is the problem worse when the engine's warm, cold, or doesn't matter?: It doesn’t seem to matter. I think it seems to start easier when it's cold...

Wow, these were great questions. I hope that I gave you some comprehensible answers?

I look forward to solution,
Kevin

well it then could be just needs a good tune up.


**changes are here**

Good description, thanks.

There are few components which cause "mystery" groupings of symptoms and parts. A bad lobe on a cam, for example, can cause a misfire at idle while showing only slightly low cranking compression and almost no driveability symptoms while running. A faulty O2 sensor can cause strange driveability symptoms with rich engines setting lean codes, lean engines setting rich codes, or other strange problems when the engine is warm. A plugged catalytic converter generally causes low power, poor acceleration, sometimes apparent rich engine operation, and possible strange exhaust sounds. In your case I originally wondered about a sticking IAC but now I'm questioning the condition of the intake manifold and valves in regards to carbon deposits, and I am wondering if the EGR valve is not closing fully at idle. EGR at idle is unwanted as it causes fresh intake charge dilution and inhibits combustion. During cold engine operation the AFR is somewhat rich which may allow more fuel to react with available oxygen. As the engine warms up and the AFR is leaned out there's less fuel available to burn. If the oxygen content is replaced with inert exhaust gas then it's harder for the engine to burn fuel fully and to create heat in the chamber. Once the ecm commands closed loop the O2 sensor will report that the engine is too rich which will cause the ecm to remove more fuel, which will make it tougher for effective combustion to occur. As the engine is run longer and longer with this problem, carbon deposits can form in the chambers, in the intake, and on the backside of the intake valves.

You might try something simple. If your hands can reach the EGR valve, first disconnect the vacuum line and confirm that there's no vacuum to the valve while the engine's at idle. Obviously if the engine runs better as soon as this line is removed you've found a big clue. But if you can reach your fingers under the EGR valve, then lift the diaphragm slightly and release it while observing engine operation. Sometimes several repeats of this can be enough to dislodge any carbon holding the valve open.

HTH

-->Slow

Well,
I went for a trip to the wrecking yard today because my EGR valve was stuck and I actually found a brand new one there. The one that was in there wasn’t holding pressure. I also got most of the sensors as well. I then came home and replaced everything that I had gotten. Now it really runs like crap!

So I think this is now beyond my scope of knowledge. So it's off to the "pro's" tomorrow...

Thank very much for all of your help, I was very much appreciated!
Kevin

You replaced all your sensors with ones you got from the junkyard?? Wow.. That's kind of crazy. You should have hooked up the new EGR and tested to see if that fixed your problem, without replacing any other sensors. If it really runs crappy now, then you probably put some bad junk on your car.

I've always replaced or adjusted one thing at a time. That way I have a baseline and will either tell if what I did helped or made no change.