majadunkel30

Mercedes CLA rough running and exhaust smell

I'm experiencing some difficulties with my 2017 Mercedes CLA, gasoline engine, which now has 205614 km on the clock. The check engine light illuminated recently, and the engine is running rather roughly. I've also noticed a distinct exhaust leak and a strong exhaust smell, which is quite concerning. Could this be related to the DEF fluid system, or perhaps the particulate filter? I've heard of catalytic converter issues, but I'm hoping it's something simpler. Could a malfunctioning oxygen sensor cause these symptoms?

4 comment(s)

Rough running and exhaust smell? Is your fuel consumption also high? It might be an oxygen sensor playing up.

Yes, I've noticed the fuel consumption has increased slightly. If it is the oxygen sensor, is it likely to affect the exhaust treatment system and cause all these problems? How difficult is it to diagnose for sure?

An oxygen sensor issue can definitely mess with your exhaust treatment. Regarding diagnostics, it's probably best to get it checked at a workshop to confirm.

Thank you for the advice. I took it to a workshop, and they confirmed it was indeed a defective lambda sensor, which they replaced. The repair cost me 375€. The car is running smoothly again, and the check engine light is off. I appreciate your help!

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