Idle 450 SEL
 

Hi

Help! I have the 450 SEL with 4.5 Litre engine. Engine is reving at about 1500 rpm on standard idle and about 1000 with car in D and foot on brake.

I am sure this is too high. Is this difficult to adjust?

Thanks for any ideas.

Mike

You have an idle adjustment screw in front of the fuel mixture assembly. Turn clockwise to reduce air flow and counter clockwise to increase.

If this does not have an effect AND assuming this only happens with the engine warm, then you may need to replace the auxillary air slide/valve. I just did this on my '79 450SL. With the engine coolant temperature reaches a certain temperature, the air slide does NOT introduce additional air into the mixture. If the valve is not closing then additional air is introduced THUS the faster idle speed.

There's also a balancing act between the fuel adjustment and the idle adjustment. The effect of having too much air when warm can vary depending on whether you're running too rich OR too lean...

btw: I learned all this from SteveFl's postings on the CIS fuel inject systems, etc...