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Q: Rough idling and lacking horse power - 1982 Mercedes Benz 380SL

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I have a 380SL that sat around for 9 months and has some engine problems. The odometer is broken, so I don’t know the mileage on it. I have quite a few vacuum leaks. I put in all new fuel injectors, gaskets, hoses, spark plugs, leads and a distributor cap. I checked the distributor and a many of the valves. Everything seems to be working OK. My friend helped me hook up the pressure gauges and set the fuel pressure of the warm up regulator and set the timing. It passed the smog check in California. So my car runs the way it’s supposed to when I start it from a cold start. It gets good idle rpms, fuel economy, horsepower, temperature, etc. It’s perfect! But when I start the car after the engine has been warmed up or hot it idles rough with a wave of rpms, awful fuel economy, hardly any horsepower and almost does a complete stall. It does this consistently. I was thinking it might be the ignition control unit, temperature sensor, over voltage relay, O2 sensor or something else. Do you have any ideas on what might be wrong?

Hello. There could be a problem with the coolant temperature sensor. I would also suspect that there could be a problem with the ignition control unit. The fuel pump could also be contributing to the problem you are experiencing. If the fuel pump is weak or not getting the proper voltage, this may cause a problem like the one you describe. Have a certified technician, like one from YourMechanic, diagnose the rough idling in order to make necessary repairs.

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