BMW 8 Engine Light + Poor Performance: Knock Sensor Issue?

Hi there! I have some experience working on BMWs. Actually, I went through something very similar with my 2017 BMW 6 Series. Had the exact same symptoms you're describing, engine light, poor performance, and rough idling. Took it to my regular workshop and it turned out to be a loose connection in the knock sensor wiring harness. The mechanic found that the plug was barely hanging on! Total repair was 95 Euro to fix the connection and clear the codes. The car's been running perfectly since then. But before jumping to conclusions, which engine variant do you have in your 8 Series? Also, have you scanned for error codes? This info would help to confirm if we're dealing with the same issue. Just sharing from my experience with the 6 Series, but these symptoms could point to other issues too. Let me know those details and I'll try to help further!

Thanks for sharing your experience! My car has 85784 KM on the clock and just had a service last month. You might be onto something with the knock sensor wiring. I haven't scanned it yet, but I have the B58 3.0L engine. Been meaning to get it checked but wanted to gather some insights from the community first. Did your car also hesitate when accelerating? Mine feels like it's holding back, especially between 2000-3000 RPM. Really curious if fixing the wiring solved all those symptoms in your case. Might head to my mechanic next week if this doesn't resolve itself, but your experience gives me hope it's just a simple wiring issue rather than something more serious.

Hey again! Yes, my 6 Series had that exact same hesitation you're describing, it was super noticeable in that RPM range. I remember feeling really frustrated because it felt like the car was fighting against itself when trying to accelerate. Since you mentioned you've got the B58 engine, it's even more likely we're dealing with the same issue. My car had around 78000 KM when this happened, so we're in a similar ballpark mileage-wise too. And yes, fixing that loose wiring connection completely solved all the symptoms, the hesitation, poor fuel economy, rough idle, everything. It was such a relief that it wasn't anything major. The mechanic showed me the connector and it was barely making contact due to some vibration over time. Just a heads up though, even though it's likely the same issue, definitely get those codes scanned to be sure. My mechanic said these symptoms can sometimes be caused by other things like fuel injectors or coil packs. But given how similar your symptoms are to what I experienced, I'd put money on it being that knock sensor wiring. Let us know what you find out when you get it checked! Always good to share these experiences so others can learn too.

Thanks so much for the detailed follow-up! That's really reassuring to hear that fixing the wiring sorted out all those same symptoms in your car. You've actually made my day a bit better, I was worried I'd be looking at some crazy expensive repair. I've gone ahead and booked an appointment with my mechanic for Tuesday morning. Will definitely have them check that knock sensor wiring first before diving into anything else. You're right about getting the codes scanned too, better to be 100% sure what we're dealing with. Really appreciate you taking the time to share your experience in such detail. Will update the thread once I get it sorted out. This is exactly why I love our BMW community, always helpful with real-world experiences! Thanks again!