Sticky idle control valve could cause this. Check resistance of idle valve coil, should be between 7 and 10 ohms. At idle, about 600 ma current should be flowing thru the coil. Idle valve receives its voltage via the OVP relay, clean the contacts at the OVP relay socket. Also check the idle switch on the throttle body, the computer needs to know that you are in idle mode, this switch must be closed when idling and opens as soon as you depress the pedal. Check air sensor's resistance between pins 1 and 2 (with car off), this should be between 1 and 2K when the plate is all the way to the top. With car on, check the voltage of the center terminal (note that the cable connector must be connected to the sensor for this test), at idle should be between 0.5 and 1V, ideally 0.7V, if not, there is an adjustment screw, higher this voltage, higher will be the rpm.

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Saumil S. Patel