I can't seem to find anybody to help me on a problem Ive been having with my car running rough. I already changed the trans because it was throwing a code for a bad solenoid and when the pan was down there were chunks. I replaced the coil pack , plugs, wiring in the housing, rubber inserts and springs and the housing also. I didn't change the coils or the ignition control module though. It starts out with the RPMs kind of jumping a bit then the car starts to putt. Listening to the exhaust it sounds like a putt putt sound like a loppy cam, very steady and rhythmic. This is in idle. While driving the RPMs flutter around and the car lags some as it does that. While in idle the ETS light came on as it was idling rough. I was told it could be a clogged cat. Then the dealer said that would show a code. I have a code reader and it shows no codes. The dealer said that if it was the cat it would show a code and I wasn't reading it correctly. A parts dealer said it was a bad computer, EPM, PCM or something. He said the ETS light meant something could be wrong with the traction control system and that would not show any codes though. There is no sulfur smell from the car although I did hit a big rock with the cat recently and that could have knocked something loose to clog it. This problem was around before hitting the rock though. If I bang on it there is a little rattling from something in there. This problem stopped when I changed the Ignition module out for a new one when I was replacing the trans a few months ago. I put the old Ignition module back in and it remained OK. I left the old one in and it had run fine and now the problem is back. Could this be an ignition problem? short? clogged cat? I thank anybody that can give any input. If somebody can figure this one out before I get to the dealer I will write a check for $30 and send it to you. I am desperate. I know when I get there there they are going to rape me ($70 an hour) because it will take so long to figure out whats wrong. No kidding on this I would rather give to somebody here than those crooks.

how's your fuel mileage? is it lower or higher now than when your car ran good? also what mods do you have in the car? Also what year and model is it?

While I am not familiar with the '99 Cav. having an older '96, I do know that sometimes older cars O2 sensors can go without throwing a code.

As long as your car is drive-able, not making horrible metallic sounds or running really hot, I think I would just drive it really easy for a while until whatever is causing the intermittent problem really fails and triggers a code. Otherwise you are just guessing and throwing your money away. If you had a lot of money, you could afford to blow it on some grease monkeys education (taken while he charges you to learn how to fix your car).

Not the ideal way to treat your car, but a necessary sacrifice if you don't want to get "raped".

It's a 99 Z24 and the gas mileage has been around 20-25 mpg since new, never changed. The only mods are an intake done long before the problem and a recently I put an underdrive pulley in but that was after the problem occured. It did throw a P0302 #2 misfire today. Can a O2 sensor cause a misfire? At the time it started this problem months ago it was throwing a P0300 random misfire. I changed the ignition module for a new one and it fixed it and just out of curiousity put the old one back in it was still OK so I kept the old one in. Again that was months ago so I can't see how if it was the ignition module it would take this long to misfire again. Is bad gas a possibility? The P0302 misfire could also be a clogged injector. At the time this all happened originally I pulled them all out and cleaned them.

Hi Jay

please don't write any checks-surely we can help here for free.!!

How about putting the new ignition module back in if you can, symptoms sound the similar to a Buick I was involved in, where a new ign module cleared the fault.
In the first instance a coil was changed but the new coil was blown again by the faulty module, so eventually it needed another coil and a new module.

O2 sensor is a possibility


I have also changed a crankshaft sensor when it juddered at any speed whilst not accelerating or decelerating, after replacement the car has always run smoothly.

anyways let us know how you fix it

Good Luck


Alont

Alright few things come to mind here after readig with this.....

Like someone said a crank sensor going out can cause this

An ignition module and even coil can cause this


You said have a misfire, lots of things can cause a misfire, coil, module, plug, wires, injector, intake or exhaust valves
With the exhaust sound you hear at idle a bad valve isnt out of the question either.






- 2004 Cavalier - 124k, owned since new

OK now I replaced the coils, battery and the ignition module. The whole ignition system is now all new. I bought the upstream O2 sensor and the crank sensor is next on the list I guess. How could I tell if its the valves? After replacing the coils and ignition module its a little better but still there. Its not throwing a code now again. The crazy thing about all this why did it go away for months then come back. Thanks to all for the input.

You can tell if it is the valves by doing a cylinder leak down test.

If you dont have a leakage tester then it has to be brought to a shop.






- 2004 Cavalier - 124k, owned since new

Well it's a cylinder 2 missfire so you should be looking at #2 cylinder you said you've changed all the ignition stuff and you were cleaning the injectors at the time maybe check all the clips on the injectors and the one big one. Sometimes the prongs inside the clip bend. or it could be a bad injector.