89 cavalier backfireing, tried evrything, please help!

[wjhjr420]

I have an 89 4cyl 2.0 cavalier with about 80,000 miles on it. The car ran excellent, then a couple weeks ago, started backfireing, and stalling. It ended up blowing apart the muffler. I replaced spark plugs + wires, and I replaced oxygen sensor, fuel injector, and muffler..lol, and I did a compression test which showed everything OK. Car starts and runs great, but once you try to drive it, it backfires and tries to die. I am thinking its a stuck or burned valve but it isnt but its pushing 160psi on the compression stroke on all cylinders. Any other suggestions are appritiated cause i am not looking forward to doing a valve job and having the same problem after.....

[wjhjr420]

i finally figured it out it was the map sensor...but only after i changed the injector,o2 sensor,ground strap,plugs wires ,ect.... but its runs like a champ now yay..

[wjhjr420]

Ok I was wrong. It ran like a champ for about 15 mins then started acting up again. It is still trying to chug out and backfires every time you step on the gas. I have checked and replaced everything I can think of. Does anyone else have any ideas? Please please help!

[gaslady]

have you had the catalytic convertor checked? i used to have an 86 that started bogging down and back firing at 127,00 miles. even two chevy dealerships couldnt figure it out. we went through all the sensors etc also.drove it till it blew engine then i pulled engine had it rebuilt. when i put new engine in it idle great but backfired and died when you revved engine. guy who rebuikt engine suggested sensors which i replaced every thing under the hood when i changed the engine. after talking to other people he called me back and asked me to take convertor off. no problem after that except a 200 dollar convertor. maybe worth having a shop check it

[gaslady]

also was a costly lesson since it blew the engine.

[public]

You can check for excessive backpressure by removing the O2 sensor and attaching a pressure gague then running the engine. This will see if you need the cat. If that is not it then check the EGR valve. The EGR is vacuum operated and the diaphram is rubber and prone to dry out and crack. This chances the entire fuel/air ratio. You can get to much or to little exhaust gas and the vacuum leak gives you too much air. Good luck.

[wjhjr420]

Thanks everyone I fixed it i had a cracked coil, I found this out after i started the car and hosed the engine it died so I pulled the coils off replaced them and its been 2 weeks now and not one single problem. If any one has to do this it is a pain to get to but they are only about 25 dollars a piece...my 4 cyinder needed 2 a 6 cylinder requires 3. FYI.

[wjhjr420]

Originally Posted by wjhjr420

Ok I was wrong. It ran like a champ for about 15 mins then started acting up again. It is still trying to chug out and backfires every time you step on the gas. I have checked and replaced everything I can think of. Does anyone else have any ideas? Please please help!

I took off the converter long time ago I found out it was the coils were bad unfoutunatly they were about the cheapest things to replace and the last thing I had thought to check......Thats how it goes

Thanks
Walt

[STINKINLINCOLN]

I never heard of a coil making it back fire but that might just be me
glad to hear that you fixed the problem

[public]

Yeah, My 89 had the bad coil thing a while back. Rigth now I have the head off and so I can get to everything. I was wondering about extending the crank sensor pigtail so I could relocate the entire module/coil assembly. The other plugs have plenty of extra length. Has anyone seen this done or given it some thought. Tis would make coil/module swaps a 5 minute repair. The whole head is only about 3-4 hours but doing just the coil or module is a real pain. With two Cavi's and one with 300,000 miles I've done a couple, and it ain't fun.

[wjhjr420]

I have never heard of that being done. I think it would work as long as you had a good ground on the back of the plate........

[public]

Well I chickened out. Actually just wanted to get it out of the garage, so I put it together stock. But I still may move that whole module assembly. It would be so easy to get to. I was kinda worried about the output signal from the crank sensor. I dont know if the additional wire lenght/resistance would chance the signal in any way. Maybe a project for after the inlaws leave. It is running great now, started right up. Engine is nice and clean inside and I have never used synthetic oil, always changed it at 10,000 miles or so :-). Perhaps if I was racing, but then I would not have a Cavi.