1982 500SL - low power

Pull the plugs and have a look at them. it could be that one or more of the plugs is getting oil fouled... Then when you restart the car, you have none of the advantages and a cold start (ie moree fuel and higher idle speed), so you are noticing the engine misfiring. Once the plug heats up enough to start firing properly, it runs smoothly again.

Just a theory, but a relatively simple one to test.

Marty

It does idle a little high, maybe around 900rpm. I'll have a look at the plugs for a start. I can't say that I've noticed any misfiring though.

This is nothing more than a stab at your car's problem, especially since it's a gray market vehicle.

I suspect the engine's control computer is misreading either the engine's temperature or the O2 in the exhaust or throttle position but, as I wrote, its only a stab at the problem. This problem is engine control related, not just a simple vacuum leak.

It's OK if you start it cold and drive continuously for a long distance but NOT if you stop for gas etc. and then restart it.

This won't be easily found. If the engine is not hot BUT the computer believes it IS hot then a lean air/ fuel ratio will be put into the engine. A faulty temperature sensor might be the cause. Or a bad O2 sensor.

The throttle position sensor is less of a suspect as the problem only occurs during warm up.

You won't solve this so find a shop that understands the difference(s) between the USA spec and gray market spec cars.

I was looking for vacuum leaks yesterday and came up with nothing. I did discover that one of the wires to the cold start valve wasn't connected very well. But, I don't think that was the problem though. I'll replace the O2 sensor since I have no idea when it was last changed. I'll also try disconnecting the temp sensor while the car is idling to see if anything happens. If I remember correctly from my Volkswagen, if you disconnect the temp sensor and nothing happens to the idle, then it isn't working. I could be thinking of something else though.