my 80' 450sl has developed an odd pattern. In the morning, the car runs great and at normal operating temp, the car runs great. However, if I drive the car at all, then park it for any length of time (5 min-5 hrs?) the car runs vary rough and seems like it's loaded up until I can drive it hard and blow out the carbon. It generally "relieves" itself with some dark smoke around the first gear shift then it's fine. Any ideas?

Two things.
1) you may have a fuel system leak down, this causes the fuel mixture to be off.
2) leaking oil into the cylinders via the valve guides

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Benzmac:
Donnie Drummonds
1991 GMC Syclone
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

The car basically doesn't use any oil at all. The problem seemed to start after I had it at the dealer for a tune up at which time they went through the fuel delivery system. It was determined that I needed a idle valve replaced but I've not had that done yet due to the cost. Would this cause the problem?