This is not a Camaro question, but it does have to do with a Chevy 3400. I have a 2001 Impala that has an occasional rough idle. It's not a *terrible* bad rough idle but noticable all the same. It's been back to Chevy three times and they have replaced the fuel pressure regulator, reflashed the PCM, and done an injector cleaning. The problem still persists and they haven't been able to find anything.
Anyone else have problems with this motor exhibiting a rough idle or is it just the nature of the beast.?

 

depends on what you mean by rough idle. one persons rough idle could be anothers smooth and steady. you should get a recording of the exhaust -- by the tailpipe, or wherever the exhaust can be heard loudest.

also try to note - is the roughness intermittent, or is it steady.
like...1-2-3-4-5-rough, 1-2-3-4-5-rough

or is it 1-rough-3-4-5-6, 1-2-3-rough-5-6, etc etc..

 

Have they ever tried replacing the wires?

 

no, but i believe if it were a bad wire it would show up in the computer as a misfire condition, and there are no codes present. Most annoying thing is it's an intermittent situation, almost feels like avacumn leak but there's no evidence of one. Frustrating at best

 

Perhaps you should check the ground to the block. It may be coming loose.

 

the problem with this is that it could be anything. your car is a OBD-II car, which makes it harder to diagnose by just saying "its that" cause the computer has a fit anytime something isnt right.

check your:
plugs
wires

clean them if able/necessary
if the dealership checked the car and found nothing wrong, then the coilpacks/ignition module should be fine, as well as the sensors, as these would set a troublecode.

now here is the pisser:
the ECM CAN set trouble codes without displaying a light on the dash. my car did it for about a year. had to get me one of the Auto X-ray devices to check it. very handy thing. i highly reccomend it. you might wanna get one as it will let you know exactly what the dealer sees when they do a diagnostic.

anyway, go that route. if it doesnt work..well.. you might wanna check out the w-body forums. they might be able to help you more (w-body is grand am i think, but its closer to your engine than what we have here)

 

ya, i have a 96 Z28 which is also OBD-II and i know that route. I was about to buy a software package to do some diagnostic/tuning stuff for the Camaro, excellent idea to check the Impala as well.
Thanks for your suggestions !