We have recently developed an erratic idle and I can?t seem to find the cause although we did find a vacuum pot under the throttle body (that sits directly under the idle adjustment screw) that is NOT connected!?!?! I am unsure of where this would connect, can post pictures if it will help, I can?t find a disconnected vacuum port or a leak although some are capped? I do not think this is the cause as the idle was always stable but now it fluctuates. One minute the idle will be a perfect and smooth 750rpm then it will jump and sometimes stay at 1200rpm, maybe the ECU is trying to make up for the disconnected line. I have checked all connections, timing, and for vacuum leaks, nothing.
I realize there could be a lot of different causes but hope that somebody might have a suggestion on where to start or probably culprits.

Thanks for any help.
Bob

 

i had a very similar problem. with alittle throttle "blip", will the idle drop down ?Many mechanics were stumped, but one said it could be the TPS sensor. sounds like you might be in the early stages of what i had.

 

The dash pot does have a vacuum tube coming out of it, but it does not go anywhere. That is how it is supposed to be. It basically keep the engine from backfiring when you let off of the throttle. It probably needs to be adjusted or replaced. Sometimes they stick.

 

Thanks, will sheck for sticking and adjustment.