I have made numerous adjustments to the mixture screw on both my 89 and 92 300CE and the results have been quite dramatic. This adhustment effects a lot more than just the idle. It seems that you have to find just the right spot to get the best combination of idle and accelaration. In both cases, the best accelaration setting was not the best for the idle but I prefered the improved throttle responce in any case. Unless I have missed it, I have not seen a lot of correspondence on this site regarding how this adjustment REALLY effects this type ot fuel injection. I did not have any analyzers - it was many trial adjustments to get it right. Getting the little steel ball out of the housing on my 92 was a *****! I had to drill 2 1/16" holes on the sides of the housing (make sure everything is covered so the chips won't end up in the wrong place) just below the center of the ball and pry it out with a long pointed punch. I had to let penetrating oil soak in for a couple out hours also. Not for the faint of heart but there was no harm done and it goes like hell now. Got to do it to my wifes 1990 300SL next.
Futher fellow owners experiences with this adjustment would be appreciated. Craig

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90 300SL Pearl Gray
92 300CE Smoke Silver