Hello I am new here and I have searched the net a lot and I have found many discussions on fast idle and rough idle I have no Idle. The only way I can get my car to start is to slide a business card in the throttle body plate thus creating a gap. The car will then start and idle ( not the best but it will idle ) if I remove the card the plate closes and car stops. Its a 1979 450sl with 111,000 miles. I recently bought the car and it was sitting for 5 years, I suspect because of this problem I want to add that while its idling I can turn the idle screw and can hear a change in the sound, the rpms do not seem to change but the sound does. If I unscrew it and try to lift it out there is significant vacuum at least to that point. While it is idling I can move the throttle linage and the car will respond but again if I remove the business card and throttle plate closes car stops.

 

sounds like you are trying to adjust the wrong thing..

 

I am turning the auxiliary air adjustment , its about the size of a dime. Last night I tried to start it and again no start, then I propped open the Throttle plate the thickness of a business card and it started and idled some what.

 

Okay I admit I am not a Mercedes guru but I have turned a few bolts. I have shipped jeeps all over the world and sent a aZ28 to a museum in Australia and a TR4 to Germany recently. I am surprised that when I said I had to prop open the throttle plate no one mentioned there is a screw that does that.!! Well my screw is missing and that is why I did not see it and why my throttle plate is closed. I am trying to find the proper name of the screw and a place to buy one. Any one have any thoughts ? It appears to be the mixture screw but I do not see a listing for it online.