Q: Mercedes 380SL starting up, rough idling, then cutting off and dying

asked by on September 25, 2017

Hello, when i start my 81 380sl it will start up, idle very roughly for about 45 seconds then shut off and die. I’ve been having fuel related problems and replaced my fuel pump and relay recently. Also when it starts the car will shake at the same time that my oil pressure gauge is fluxuating from normal to very high. I put new gasoline and the gas renewing formula in my tank and it made it idle a little softer but it still shut off, but this also made my oil pressure gauge much more steady and normal. Any thoughts? The car drove and run yesterday. Thank you

My car has 112000 miles.

The mileage is not that high but due to the age, before attempting further diagnostics, you should test cylinder compression and intake vacuum (to check for stuck valves). If you determine that the engine is basically mechanically sound, there are lots of possibilities, one of which is plugged fuel injectors, again due to vehicle age. If the fuel injectors on this vehicle have not been recently cleaned, they should all be removed from the fuel rail and sent to a lab such as Mr. Injector for service. Typically these injectors have a miniature filter basket that is replaceable. Cleaning injectors on a car is a waste of time and money and the injector itself has to be cleaned ultrasonically in a cleaning fluid and, as noted, the filters must be replaced. In addition, they must be flow tested. Prior to removing the injectors, it is possible to use an oscilloscope to look at secondary firing patterns to distinguish between fuel versus ignition trouble. If you desire that this problem be diagnosed by a certified Mechanic, dispatched by YourMechanic right to your location, the recommended service is a rough idle diagnostic. If you request that service, the responding certified mechanic will get this resolved for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

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