The idle speed has been creeping ever upward. I jumped into it today and found that if I pinched the hose between the aux air valve and the idle speed screw, the idle would drop.

The idle speed screw is all the way in and there are no vacuum leaks that I can find. I pulled the aux air valve and heated it with a heat gun till I couldn't hold on any longer and it didn't close all the way. About 3/16" gap remained. I tried lube and carb cleaner but it still didn't close all the way. My Bosch fuel injection book that if I pinch the hose at operating temp, the idle should not change, which tells me the valve should be fully closed. What do you guys think?

The valve is $424 Any body got a spare?

Michael

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Usta haves '69 250/8, '76 280C, 1971 250C 114.023, 1976 450SEL 116.033
Current have, 1983 300SD 126.120

I think you have a great opportunity to figure out how to fix a chronic problem on these engines. See if you can take it apart, try various cleaners and lubricants, and report back to us on the results!

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe

Chronic problem?? Argh.

The valve has a 30 degree marking on it so I think it should be full closed at 30C. The car started this morning but was a bit cold blooded like my 250C.

I'm goming to start looking for a good used one.

Michael

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Usta haves '69 250/8, '76 280C, 1971 250C 114.023, 1976 450SEL 116.033
Current have, 1983 300SD 126.120