I have a 1981 380SL which idles very fast (about 1500 rpm) when started up after it has has not been run for awhile. If I remove the wire from the idle control unit at the idle control valve while it is idling at the fast speed and then replace it, the idle speed drops to about 700 rpm and will stay at that level for a lengthy period of time (usually the remainder of the day).
Would this possibly indicate that the idle control valve should be replaced or is it more likely the idle control unit that is defective?