Recently our 450SL (48,000 miles) started demonstrating an engine miss at idle and a cold acceleration stumble/hesitation. The engine misses until the temperature comes up to above 60 C on the temperature gage and then it works and drives fine. It is most noticeable when accelerating when the engine is cold. Previously the engine started and ran fine at all temperatures. The car has a new (~1 year old) acceleration warm up compensator on it so I suspect that this is not the cause of the engine miss. It appears that there is some part of the enrichment circuit that is not happening correctly which goes away once the engine warms up.

Two questions:

1) The car has the original plug wires and cap/rotor. Could this be causing this problem? They appear to be in good shape and there is no evidence of any cracking or burning in either the rotor or the wires. The humidity here in Wisconsin is not bad so I do not suspect that this is the cause.

2) Is there an order that I should follow in trying to diagnose this problem? Several items that could contribute towards this would be the thermosensor, the oil temp sensor and/or the water temp sensor. How do I check these or should I check something else first?

Appreciate your help with this. It's a great car (once the engine is warmed up!) and would like to resolve this prior to the short summer driving season.

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Jim Loseke
1980 450Sl "Black Beauty"
2002 C230 Kompressor "Spicy"