Fast Idle Issues
 

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?

One thing to check. When you get the high idle, slide the connector off the pins on the valve a little ways, and use a meter - carefully - to measure the voltage going to the valve. If it shows somewhere around 4 volts, the relay is trying, so replace the valve. If no voltage, replace the relay.

Thanks!
 

Thanks for the suggestion. Went out to start the vehicle tonight to check the voltage as you suggested and the car started and is idling properly. I'll have to wait until it acts up again to check it out. Will let you know the results.

Thanks again for your interest and help.