Overheating and accelerating on its own on 1999 Pontiac Grand Am

Recently my car has been trying to overheat when it has antifreeze in the reservoir. Also it has been trying to accelerate on it's own and when I put it in park or neutral the rpms rev up between 3 and 4 thousand rpms. The throttle is not sticking and the pedal is unobstructed. Where should I begin to try to fix this problem?

Asked by for the 1999 Pontiac Grand Am
You need to put a scanner on this vehicle and see what code comes up, I think autozone still does this.
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My '99 does the same thing. Please let me know if you find out what causes it.

Typically, all I have to do is turn it off and restart it. Most of the time that seems to do the trick.
IAC sensor does it. just replaced mine today and the car doesn't accelerate on its own anymore...