What causes the lean mixture in cylinder 1 of a Mercedes-Benz C200 at idle?
2 Answers
Mercedes-Benz C200 at idle when the mixture cylinder - too lean causes are as follows: Intake system air leakage: Can lead to a lean mixture, it is recommended to check whether the oil dipstick is inserted tightly, check whether the oil cap sealing gasket is aged, and check whether the exhaust valve is damaged; Incorrect air-fuel ratio: Resulting in a lean mixture, it is recommended to check whether the throttle is dirty, as dirt can also cause a lean mixture, check whether the fuel injector atomization is good, if it is equipped with a direct injection engine, it is recommended to clean the fuel injector, because the direct injection engine fuel injector is not easy to disassemble so it is difficult to observe, it is recommended to check whether the engine computer has any fault codes related to the oxygen sensor.
I've encountered this issue quite often with the Mercedes-Benz C200 – cylinder 1 running too lean at idle, which essentially means too much air and not enough fuel, leading to rough idling or sluggish acceleration. Common culprits include vacuum leaks, such as cracks in the intake manifold or loose fittings, allowing unmetered air to disrupt the air-fuel ratio. Another possibility is clogged or aging fuel injectors, restricting fuel delivery and causing a lean condition. A faulty mass airflow sensor can also send incorrect data, resulting in uneven fuel distribution by the ECU. From my experience, carbon buildup can trick sensors into misreading, so regular throttle body cleaning helps mitigate this. Start with basic diagnostics: use a smoke test to pinpoint leaks or scan for trouble codes (often P0171 for cylinder 1 lean) via OBD. Don’t delay—visit a Mercedes specialist for precise testing. Safety first.