Having high idle problems on my '83 380 SL. Hopefully someone can point me in the right direction.

Replaced the Idle Control Unit, the Overload Protection Relay, Idle Control Valve and vacuum hoses, along with the 42 degree C Engine Temperature sensor. Get 13.4 volts at ICU Connector pins 2 and 4.

Tested voltage at the Idle Control Valve connector and get about 11 volts.

Idle Control Valve clicks when tested.

Took the car out on an errand yesterday and when I started it up to go home high idle was gone.

Unfortunately whatever caused the idle to work was only temporary.

I'm stumped. From everything I've read it should work correctly.

Anyone have any suggestions on what to try next?

Thanks
Mark