Cold weather idiling....engine speed.

I started my 2003 Pontiac Grand Prix GT 3.8 Series II 120K miles on it. It was about 30 degrees Farenheight this morning. The car usually idels at about 1500 RPM's on a cold engine for a little while and then goes down in idle speed. I noticed this morning though that it stayed at 1500 RPMS for a looong time until i hit the gas pedal and then it went down to normal idle. What could cause this problem, bad throttle sensor mabey?

I would first check the IAC valve to see if it's carboned up or sticking.

With 120K miles try cleaning the throttle body including the butterfly plate. High idle is caused by high IAC counts. Could be the TPS or Idle Air Controller (IAC) but a flaky TPS normally throws a code. I agree clean the IAC and the seat at the TB where it mounts.

ok, thanks i was figuring on those....i'll clean them up and let you know how it goes. Although i did start my car this morning in similar weather temperature and it warmed up fine with proper Idle speed adjusment with engine temp. Thanks though

i have just one other question.....i guess i am fortunate to have a Grand Prix with 120,000 miles and not have had the serious transmission problem most of these trans have with that pressure control valve or something......do you think it is bound to go bad with this many miles, or since it has this many miles it probably wont, and probably would have already happened by now if it were going to go bad?

....do you think it is bound to go bad with this many miles, or since it has this many miles it probably wont, and probably would have already happened by now if it were going to go bad?

Don't worry about it unless you get tranny issues. The 2003 and up are supposed to have the revised PCS and valve body mod.

The only thing i can say it does is.....when on the highway for a while and then getting off the highway and now you have to start shifting alot with constant stops at stop signs it will go into that "hard shift" mode for a few mintues. Only happens when i go slow though like, it will get confused weather to stay in first or second gear, hard to explain but then goes away after driving a little bit.

Hard shift mode? Confused? High idle? ..... Clean the T-body and iac as mentiond, but it might not hurt to do an ohm sweep on that TPS also.