Sounds like idle control motor. Disconnect connector. Check resistance at motor side of connector. You should have the following or the motor is defective.
Between green wire with red stripe and green wire with black stripe--------28-33 ohms @ 70 degrees F
Between gray wire with black stripe and green wire with blue stripe--------28-33 ohms @ 70 degrees F
If this checks ok, check your TPS for sticking or high voltage at idle.

Over the hill but still climbing.
88 Montero 2.6L auto, manual hubs, cooling fan conversion gps,recurved distributor,LSD Diff.