Well, I replaced the idle control valve. It looked like this fixed it. But, the next day I had the fast idle again. Its back to intermittent.

Yesterday, I got frustrated with it. I had been hearing a hiss from behind the outlets in the center console. I started disassembing to try to find a broke hose or something. In the process I took out the climate control unit. When I started the car perfect idle. The rest of the day, perfect idle and no hiss. So I figured something the control unit activates has a vacum leak. However, my wife took the car out and again the fast idle is back.

Disconnecting the connector from the idle control valve no longer causes the idle to speed up, nor does reconnecting it cause the idle to slow down.

At this point I'm at a loss.

Anybody have any ideas on what this sounds like?

I would appreciate the assistance.

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1983' SL500 euro