My 450 SL with 180000 miles on her has a strange idle problem.
When cold started, the idle goes to 1500 RPM and takes 4-5 minutes of running to come down to around 800 RPM. If you pull the two wire connector from the small vacuum relay by the coolant tank, the timing will drop to 0 BTC from 10 degrees BTC, and the vacuum will then be allowed to go through the relay. The vacuum relay connector has 12 volts on it all the time. This has the effect of blocking the vac. from getting to the Dist. all the time, hot or cold.

So far I have confirmed, Valve settings, Injectors cleaned, MAP sensor checks OK, Trigger Points cleaned, Dist. points and rotor clean, plug wires ok, coolant temp sensor replaced, air temp sensor ohmed ok and timing set to 10 BTC with no vacuum.

Anyone have any other ideas??

Thanks to all,
Mark