The first thing I'd check for is a vacuum leak. The Engine Computer controls idle speed through the automatic idle speed motor which is a controlled vacuum leak around the throttle blade. It may be trying to compensate for the high idle resulting in surging. Pinch off various hoses to see if one brings the idle down. You can also spray water on the hoses and gaskets while the engine is running and still cold. Watch for it getting sucked in or listen for the speed change.
Tuesday, March 5th, 2013 AT 9:21 AM