ralf_drache1

Mercedes B Klasse Engine Running Rich

My 2023 Mercedes B Klasse with a gasoline engine, has 128567 km. Lately, the engine's been running way too rich, with reduced engine power, check engine light, rough idling, and terrible fuel consumption. It's jerking when I accelerate. I suspect a defective fuel injector. Could that cause a rich mixture and mess with the catalytic converter and oxygen sensor readings, throwing off the air-fuel ratio? Has anyone else seen this?

4 comment(s)

Sounds familiar! I had a similar thing happen with my B Klasse: check engine light, rough running, the whole thing. Did you notice any difference in how it runs when the engine is cold versus warmed up? That was a big clue for me.

Good point. Now that you mention it, it does seem a bit worse when it's cold. What was the issue with yours? Was it the fuel injectors as well? And did it mess with your catalytic converter at all?

Yep, turned out to be faulty fuel injectors. They were dumping way too much fuel in. As for the catalytic converter, I'd definitely get that checked out. If it's been running rich for a while, it could have damaged it. Honestly, I'd take it to a workshop to get it properly diagnosed. Best not to risk further damage.

Thanks for the advice! I took it to the shop and you were spot on. A defective fuel injector was the culprit, causing the rich mixture. I got them replaced, and the car's running smooth again. The bill came to 515€, but at least the problem is solved. They checked the catalytic converter and oxygen sensor, and luckily they were still okay.

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