No i wouldn't think bad stem seals could cause rough idling. And if they did, oil-smoke from the exhaust would be VERY obvious.
I replaced the coolant temp sensor in mine last year. -Got rid of rough idling and rough running.
-Later i had to replace the entire injection system, but that's another story..
Never criticize someone until you've walked a mile in his shoes. That way, when you do, you're a mile away -and you have his shoes!
'86 300E optically converted to '95 E300 (Sold)
-Blauschwarz on silver
-17" AMG & 15" AMG for winter