on my 95 gt i was having a pretty bad idle surge. i was talking to one of our service advisors about it and he INSISTED that it was a sensor (name escapes me) that keeps a cold engine running before the fuel has changed to a gaseous state. i was like ok dude, but my car does this regardless. i could have been driving it for 2 hours and sitting at a stop light and the rpms will start spiking on me then drop so low that the car actually stalls. (its an auto tranny). but my service advisor still insisted it was that sensor. in the back of my head i was thinking that it could be what one of the other guys said about the TP sensor. i asked him about the possibility of if being the tp sensor and he said absolutely not. "No, that wouldn't be the cause, and besides, the techs would have picked that up right away." so i went and talked to our engine tech and he also said that the tp sensor was fine. well i work in our parts department and my dad is the parts and service manager (sweet) so i grabbed a tp sensor and threw it in there. and what do you know?!?!?! idle surge no more!!! so guys, if you are having this same problem and the dealership keeps telling you that they cannot find a problem. just buy the tp sensor and tell them to put it in there this will very likely fix your problem.
just a little advice from my experience.

 

nm