Mercedes C Klasse Diesel Mass Air Flow Sensor Issue

The symptoms you describe certainly align with a failing mass air flow sensor. The check engine light illuminating, coupled with increased fuel consumption, idle instability, and smoke upon acceleration, are all indicative of incorrect air/fuel mixture management, often stemming from inaccurate readings from the mass air flow sensor. To confirm, have you scanned the OBD system for diagnostic trouble codes? Specifically, a code related to the mass air flow sensor would provide further validation. Consider inspecting the air intake system for any obvious obstructions or leaks before condemning the sensor outright. The electrical connector integrity at the sensor should also be verified.

I scanned it and it threw a code pointing directly at the mass air flow sensor. I checked the air intake for leaks and didn't find anything obvious. The connector looks okay too, no visible damage. Is there any other test I could do on the sensor itself before replacing it?

Given that you've already retrieved a relevant diagnostic trouble code and visually inspected the intake and connector, further testing of the mass air flow sensor without specialized equipment is unlikely to yield conclusive results. While voltage checks are possible, interpreting those values accurately requires manufacturer-specific data and a thorough understanding of the sensor's operating parameters. Considering the potential for misdiagnosis and wasted effort, I recommend consulting a qualified technician for a comprehensive evaluation. Replacement of the sensor is likely required, and they can ensure proper installation and recalibration if necessary. This is especially important given the potential impact on engine performance and emissions compliance.

Thanks for the advice. I took it to a workshop, and they confirmed it was the mass air flow sensor. I replaced it and the car's running great again. Total cost was around 365€, including the sensor and labor.