next time it does this try sticking your foot under the gas pedal and push up on it. If its in the throttle linkage/cable this might make the idle go back down and let you know where the problem is. My DD (84 toy) idles at 800 but from time to time when I come to a stop the idle will hang at 1000, if i pull up on the pedal it drops right down to 800. it happens so rarely I never seem to get around to fixing it. If the vehicle in question is carbed and the idle surges when stopped try replacing the o ring on the idle fuel cut solenoid. get one from toyota not the hardware store.
