Thread: Rough Idle, Hessitation on acceleration

Hi all, have a 97 GP 3.8 N/A that is idling very rough and hesitant while hitting the pedal. I've cleaned the PCV, IAC, MAF and EGR. I've unplugged the MAF sensor, but it runs the same while unplugged. It will die it you dump the gas pedal while parked if you have it above 1K RPM. Also, while idling I can slowely raise the RPM to 1000-1200 and try to maintain that RPM, but without letting the pedal up, it will drop back down to 800RPM. Then, if you dump the pedal, it dies, like being choked off. While idling, it will sound something like this.... hmmm chug chug chug chug hmmmm etc. Any suggestions?

Not over heating, not loosing coolant. Just went back out to see if I can describe it a little better. When you crank it, either warm or cold, it will idle perfect for a few moments at around 900-1000 RPM. Then on it's own, the idle will drop to around 650RPM and will do the hmmm chug chug chug hmmm think out the exhaust. When I make the pedal get to 1000-1200 and hold it steady there, it will quickly go back to 650RPM without relieving the pressure on the pedal. Now, when I completely let off the pedal, it will stall and die. But, when it I get it at WOT, and dump the pedal, it won't stall, but rather wind down to 900-1000RPM like it should for a moment, then drop to 650RPM again. It's almost as if the throttle is resetting itself when I slowly press and hold the gas pedal to get to around 1100-1300 RPM due to the drop back down to 650 on it's own, and when I dump the gas pedal, it dies as if it's not getting any gas.

Just checked'em, there good.

Forgot to mention too, that the gas pedal sticks sometimes as well, like it's stuck. Takes a little pressue to "break free" and let go to accelerate. I checked at the linkage at the TB and same thing there as the pedal, so not the pedal assembly.

Originally Posted by aussie

Check your fuel pressure...

Then check your CAT

Ok, stupid question here...what's the "CAT"?

DUH! Shoulda known that one. What the best way to check it, or what should I be looking for?

Do you guys think it could be the throttle position sensor? If so, is there a way to check? So far, I've ran the vehicle with the following unplugged, 1 at a time individually: MAF, IAC and TPS. There was no change in the crappy idling.

Reading other threads, and noticed someone swaping the ICM out and problem solved. It there a way to check the ICM for malfunctions b4 buying a new one to see?