02 rough idle

[Twin1]

My 2002 TB idles real rough when i put it drive, it doesn't do it in reverse nearly as bad. the rpm's don't fluctuate at all, it just has a bad vibration in drive. It has always had a slight hesitation when pressing the accelerator, but i attribute that to the TB. I have changed plugs twice,fuel fiter every 10k,air filter annually and I've changed the IAT, and i clean the MAF and throttle body every 15k. No codes . Can someone tell me what i'm missing or is it one of those parts that's broke but just doesn't give a code like a o2 sensor or coil. Help!!!!!

[maxwedge]

Rough idle can mean many things, too low an idle, noise at idle, misfire at idle, vibration can be something grounding or loose in the exhaust, someone with technical experience needs to feel/check this on site.

[Ghost916]

I have the exact same issue, did you evey find a fix?

[BRD]

FWIW, there's a recent thread over on the GMC Envoy (99% the same veh as a TB) that indicates a similar problem caused by replacement and/or disconnection of the battery for long enough to drain the PCM's power head. I'll let it speak for itself, but it is a fact that a PCM can lose programming instructions and the engine will run rough or idle poorly. Gremlins, I guess. It happened to my wife's '03 Envoy while still under warranty, ran just sluggishly enough to get it back to the dealer's. No cause of malfunction determined, PCM re-prog'd with updated software, OK since. I've puzzled whether somebody might have passed close to the the PCM with a magnetic tool - like during an oil change or the like - but for obvious reasons I don't think I'll test it at home.