2001 Venture high idle speed

I have a 2001 Cehvy Venture van that has recently started idling at high speeds after being started. It will run for a few seconds at normal RPM then jump to a fairly high RPM. WHile driving, it will h old a speed of 45 MPH because of the engine speed. I am suspectng the idle air control valve but am not sure. Has anyone seen somethng similar. If so, where is the valve located so I can check it.

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I have the same problem with my '01 venture.  Brought it to my mechanic just last week who found nothing during system scan and test drive.  It occurs during hot weather (88+).  Idle won't kick-down via accelerator but does reset after turning vehicle off but resumes high idle after acceleration.  This van has been an electronic nightmare - climate fan speeds fixed twice, rear air vent doors stuck, dash gets super hot with stereo use.  The intake manifold gasket was replaced as well (overheating and fluid loss).  Other than than that engine and drive train are solid.  Vans accelerates, handles and rides really well and hauls 8 people and tons of gear.  I hope we can get some help with that idle.  It can't be healthy for the motor. 

Mine has a similar high idle speed issue.  I haven't found a solution yet so any advice is appreciated!

I have experienced similar problems with our van.  On warm days (+75 degrees), not only does it idle excessively fast but, in slow or stop and go traffic, the engine overheats and stalls.  Frustrating on the expressway.  Our mechanic as well as local Chevrolet dealership conclude there is no problem with the engine.  Love the van but must find a solution to this problem.

My old F-150 had that problem i believe it was the IAC i really can't remember.