My 2000 4.6 will rev at a real high speed for no reason when idling. I have to step down and release the gas pedal to bring the idle back down. It does this at no specific time, out of the blue will just rev.
Is this the IAC?

 

If you need to move the petal manually id say its the cable, but it may be the IAC. work at cleaning the IAC and the throttle body.