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Old 03-07-2002, 02:25 PM
Mark Herzig's Avatar
Mark Herzig Mark Herzig is offline
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Join Date: Apr 1999
Location: Austin, Texas
Posts: 380
Rough Idle '79 450SL

I'd greatly appreciate any suggestions on what might be the cause of a rough idle when the car is fully warmed... The idle drops to around 600-650 RPMS. The oil pressure stays around the first bar which is within specs I believe.

Otherwise the car runs magnificantly. I recently had the injector seals replaced, new plugs, new chain tensioner. I also adjusted the idle screw 1/2 turn counter-clockwise. Also, motor mounts recently replaced (by prior owner).

I could not find anything specifically in the archives that addressed this problem and since I've dropped a lot of cash on this car the last 2 months, I'd like to try to fix this myself. Any suggestion would be GREATLY appreciated.

Also, what are the rules of thumb on adjusting the idle screw? How much and in what direction produces what result.
Mark Herzig
1995 E300D 153K
1985 300D 142K (sold)
1979 450SL 122 miles (sold)
1992 500E 127K (sold)
1987 300SDL 132K (sold)
1986 300E 161K (sold)
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