MikeWheels

Mercedes SL running rich diagnosis and repair

My 2004 Mercedes SL with a gasoline engine is running excessively rich at 214711 km. I'm seeing reduced power, a check engine light, rough idle, high fuel consumption, and jerking during acceleration. The spark plugs are sooty, the air filter is clean, and the OBD-II scanner confirms the rich condition. Could this be a defective fuel injector?

4 comment(s)

Sounds like a pain. Could be. Have you checked the air filter? Sometimes a clogged filter messes with the air-fuel ratio.

Thanks for the suggestion. The air filter is clean, checked it thoroughly. If the air-fuel ratio is off, and the air filter is fine, could the problem be further upstream in the fuel system, like a faulty sensor or a fuel pressure regulator issue instead of the injector?

If the filter's good, and it still runs rich, the fuel system is more likely the problem. Sounds like workshop time to me.

Thanks. You confirmed my suspicion. Took it to a shop. Indeed, one fuel injector was faulty, causing the rich condition. Replacing it, along with a necessary software adjustment, set me back 515€. The engine is now running smoothly. Fuel economy has improved, and the jerking is gone.

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