Ever since I bought my 2001 GT I have had idling problems. I replaced the IAC first with a brand new motorcraft one. Have replaced all vacuum lines, have no exhaust leaks. The car runs normal like it should when started. It is a manual and idles around 800 RPM's. After driving for 15-20 minutes sometimes the car idles at around 2500 RPM's. If I turn the engine off and restart it it will idle normal again. That is the only way the idle will drop is by restarting. Sometimes after the RPM surge and restart the idle will drop to around 400 RPM's. Could a worn out throttle body possibly be causing this? I do not want to buy one if I do not need one. I am starting to wonder but hoping its not a bad ECM. The turning off the car and restarting is making me think this. I love driving my GT but thank goodness I have another car I drive most of the time because of this idling problem. There are no engine codes.