Have an '87 190E 2.3, 80k miles with rough idle. Emission readings were 0.1% co., 450ppm hc.
Runs clean & smooth above 1000 rpm.
Can richen mixture to smooth idle, but hc. & co both raise considerably. Can not detect any air leaks. Compression test shows cyl.1-150psi, 2-125psi, 3-125psi, 4-150psi. I'm thinking head gasket, but there is no oil/coolant contamination,spark plugs all look the same and the car does idle very smooth if the mixture is richened. If the compression readings were normal, I'd look at the injectors, but cyls 2&3 look too low.
Any sugestions? Is this motor prone to valve problems @ 80k miles?