Pontiac Repair: 2001 Grand Prix idle increasing, pontiac grand prix, vacuum leak

Question
Our 2001 Pontiac Grand Prix, has started to idle at 1500-1700 rpm, sometimes after driving a while,almost like your pushing the accelerator, if we shut off the engine and wait a couple minutes and restart it's ok back to the 900 rpm we are used to seeing. It started doing it on the highway when we took a long trip, what could cause this? idle control valve, cruise control?  Help!!

Answer
Hi
Could you please tell me which motor (3.1 or 3.8)
It will aid in diagnosis.
I will tell you, about the only thing that can cause high idle on newer computer controlled vehicles is a vacuum leak. NOT saying it cannot be anything else, but vacuum is ususlly a good place to start.
It MAY also be the IAC valve.
Please follow back if needed.
Pawl