I got at it with the hood in the fully raised position with a very long, thin screw driver. You know where the oil filter is? Look for the black hose lower than the oil filter area between the filter and the engine at the very back of the engine. If I remember correctly, the tube was connected to the engine itself. Black hose with a silvery clamp holding it tight to the engine. The hose was snug but, when I put my hand on it, it wiggled just a tad. One quarter turn on the already snug clamp screw tightend it up properly.

I'm curious to know what it's called and what it does. I could be crazy, but I swear this solved the problem. It's been a month or two now and the idle remains silky smooth.

Good luck and best regards,

__________________
Michael

1988 300 SL (5 Speed)
1994 E320 Wagon
1997 C230