Mercedes B Klasse Hybrid engine running rough

Whoa, that sounds familiar! I have a B Klasse too, though I can't remember the exact year, and I had similar symptoms not too long ago. Rough running, check engine light, the whole shebang! For me, it turned out to be a cylinder misfire traced back to a dodgy fuel injector. Did the scanner specify which cylinder is misfiring? That could help narrow it down. Have you noticed any change in your fuel economy too? Mine went down the drain. I'm no expert, but it might be worth checking the simple stuff first, like the spark plugs, before you go tearing into the fuel system.

Thanks for the quick reply! The scanner did show misfires on cylinder 3. I haven't really paid close attention to fuel economy lately, but now that you mention it, I think it might be a bit worse than usual. How difficult was the fuel injector replacement? And did you experience poor throttle response too?

Okay, cylinder 3 misfire definitely points towards that injector being suspect. Replacing it wasn't something I felt comfortable doing myself, to be honest. I ended up taking it to a workshop. I'd hate for you to mess something up and end up with a bigger problem. And yes, the throttle response was terrible! It felt like the car was hesitating every time I tried to accelerate. If you're not 100% confident, I'd recommend getting it checked out by a professional. Could save you a headache in the long run.

Thanks a bunch for the advice! I think you're right; I'll take it to a trusted workshop. I just wanted to get an idea of what I might be looking at before I went in. It turned out to be exactly as we suspected: a faulty fuel injector on cylinder 3. The final bill was around 515€, which is a bit painful, but at least the car is running smoothly again!