I have an 86 300SDL om603 with 75k miles. The engine is putting out some light grey smoke on idle and i'm trying to eliminate that. When the engine is cold there is a slight lifter tick from time to time, but it runs very smooth and starts easily, but does idle rough for 15 seconds if I don't let it glow extra time. The car is in great shape and well cared for, what could be causing this smoke? the heads not cracked, no cold pressure, runs at a needle width above 80c under load and I have checked the coolant for combustion gas with a test kit.