idle speed

[ljmauricio]

My 1982 500 SL idles at 700-750 after cold start up. After engine fully warms up idle goes up to 950. Shouldn't it be just the opposite? Anybody have any suggestions on how to keep the speed in the 700-750 range after the car has warmed up?

[230/8]

From what you describe, it sounds like your auxiliary air valve may not be working as it should. This valve provides extra air and fuel from the cold start valve during warm-up. This raises cold idle speed which then gradually drops as the valve closes off in response to the rising temperature of the engine. You may be able to remove the valve and clean it with carb cleaner if it is sticky. I recall a Jag site that had some repair tips for this valve. It was also used on the V12 jag engine. Also, be sure to check the operation of the cold start valve and the thermo-time switch which work together to dump in that bit of extra fuel.

Search this site for other tips on maintaining the aux. air system, and get a service manual if you do not already have one.

Good luck,

230/8

[ctaylor738]

Does it have an idle air valve controlled by the relay like the 380SL? If so, it sounds like the temp sensor at the back of the head is doing the opposite of what it should. The sensor is supposed to send either ground or 12V (don't recall which) to the relay when it warms up and that tells the relay to drop the idle.