Cold Hesitation/Rough Intermitant Idle

[bryandj23]

Hello Everyone...

 

Got a 93 Grand Prix, 3.1L Engine. About 4 months ago, I replaced the ECM due to strange engine behavior (intermitant), and a Code 53 (Overvoltage). Since then, the car has been running fine...

 

Shortly thereafter, I noticed that when the car is cold, upon acceleration there's hesitation....almost as if the engine is going to die. It quickly recovers, however, and runs fine. This will continue after accelerating from a stop, until the engine warms up (or maybe come out of closed loop?).

 

Starting last week, at idle, the engine seems to be running very rough. A little shaky, and chuggy like. Since I'm a new(er) owner of this used car, I was thinking it's probably time for new plugs, wires, filters, etc. I thought I would check on here to see if anyone else has had this sort of problem before I go out spending money on something irrelevant.

 

Oh - I also plan on cleaning out the EGR (again), since when I was getting the 53 Code earlier this year, alot of carbon was getting built up in the EGR.

 

Any advice would be greatly appreciated, so thank you very much!

[19Cutlass94]

Try some new plugs. I had a cylinder go out on me once, it was a bad plug, but it was doing many of things your saying your car does. So new plugs and wires could help it. Does the exhaust have any kind of smell to it? Or if you put your hand over the tailpipe, does it seem like its a bump, bump, bump, on your hand and not smooth?

[bryandj23]

Funny you should mention the exhaust thing...that was my next guess.

 

Just a bit ago when we stopped for gas (and the engine was chugging), I did smell that ever-popular rotten egg smell....and VERY potent, at that. I'm not quite sure if it was our car or not. Then again, when we left the station and pulled out onto the road, I could smell it again.

 

Earlier this year, when the computer was receiving apparent "overvoltage", it would run the engine VERY rich...to the point where people behind us could get lost in the black smoke. I wouldn't doubt that the catalytic converter is shot.

 

We're gonna try the plugs this weekend, and I'll post the results. I guess then we'll look towards the converter. I had one put on my 88 Beretta back some time ago, and a local muffler shop charged me $120.

 

Thanks for the advice. I love this board!

[19Cutlass94]

yeah try the plugs first. Thats inexpensive compared to a new cat. And if it works awesome! but the rotten egg smell is typical of a bad cat...