I found what might be a $3.00 improvement to the somewhat rough idle these cars suffer. On my 1988 300ce the idle control valve connector had lost part of the plastic or rubber, whatever it is made of, and I bought a new one. When I removed the old connector and took out the wires I noticed a gap or separation in the metal plugs at the ends of the wires, causing a loose fit. I tightened each plug with pliers, cleaned the black greasy stuff out of the plugs and off the icv prongs, and reinstalled. The idle was noticeably smooother, although still not perfect. The part number for the new connector, which mb calls a pin bushing, is 011-545-71-28. Hope this helps.

When my car is at rest and in gear, the idle roughens when there appears to be a slight increase in rpms and oil pressure. Any other connectors that might be checked to smooth out the idle?

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87 300e (white/black; amg body kit)
88 300ce (red/cream; amg body kit)
93 300ce cabrio (white/blue/blue top)
93 300ce cabrio (black/grey/black top)
98 ml 320 (totaled @ 137,000 miles)
99 clk320 (black/grey/black top)