My 380SE -85 Euro had intermittant high idle about 1000r/min. I went to dealer and mech told me that idle control valve was bad. The price of valve is $600...so I cleaned the valve with carb cleaner.. after cleaning it worked properly. But the car still idled high.
Then I took out idle speed control unit, located in engine compartment between engine and the firewall. There was some components with bad soldering. After resoldering of loosen legs the unit seemed to be fine.But the high idle was still there.
Finally I studied the Service-cd very closely and there was told about measuring the condition of throttle switch. I checked the continuity, idle contact of the switch. I found no idle contact! The throttle switch was changed and idle came back to normal. The switch price was $35.