Idle Speed Control Valve Question

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2 replies [Last post]
SBolster's picture


Two days after fixing the air conditioning (finally), the 380SL began to shake at idle and under light acceleration (both with the compressor on or off).

I suspected the idle speed control valve...I disconnected the wire leads and started the car. The idle stabilized at 1500 RPM as advertised in the service manual (no shaking). I plugged the wires back in and everything is working fine!

Question--could the air conditioning have caused the idle speed control valve to stick? Since it hadn't been made to compensate for the compressor in a long time?

Another question--is there a safe way to maybe clean out the idle speed control valve? Is there maybe some sort of gunk in there?Am I making any sense? Like I said before, the car runs fine after disconnecting and reconnecting the wires, but I'd like to prevent it from happening again!


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Tom Hanson's picture
Arrowhead Farms, CA
Joined: February 20th, 1997


1970 300SEL 6.3

The idle speed control valve gets its signal from the idle speed control computer. Either one fo these components could cause the symptoms you are talking about. In most cases, both of these components get replaced becaus it's nearly impossible to tell which is bad.


Tom Hanson
Supervisor, Parts Operations
Mercedes-Benz Classic Center USA
949 598-4842 direct.

Prior MB cars: 2010 ML350 Bluetec, 2003 C320 Coupe, 1986 300SDL, 1971 300SEL 6.3, 1973 450SE, 1959 220S, 2011 C300

Former Member
kropsch's picture
Joined: March 5th, 1997



Hi Steve:

You can clean it with carb cleaner. Pour some inside the valve
and shake it. Lots of dirt will come out. No problem in doing it.

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