BMW 8 Series Rough Run: Stalling & Power Loss Mystery

I had very similar issues with my BMW M850i (2018) last year. The symptoms you're describing match exactly what I experienced, rough idle, jerking, and poor acceleration. After diagnostic tests, it turned out to be faulty fuel injectors. The garage found that two injectors were clogged and one was leaking, causing uneven fuel distribution. This affected engine performance and emissions readings. It was quite a serious issue that required immediate attention since bad injectors can damage other engine components if left unchecked. The repair involved replacing three injectors and cleaning the fuel system. The work took two full days since accessing the injectors on these engines is pretty complex. After the fix, the engine ran smooth again, power was restored, and emissions came back to normal. My advice would be to get a proper diagnostic scan first, these symptoms are classic injector problems on BMW engines. Make sure you find a garage with experience in modern BMW fuel systems, as they need special tools and knowledge to properly diagnose and repair these issues.

Thanks for sharing your experience! That's super helpful as it sounds exactly like what I'm dealing with. Really good to know about the injectors, makes total sense given the symptoms. Quick question, do you remember roughly how much you ended up paying for the full repair? Also, has everything been running smoothly since then, or have you noticed any other issues pop up? Just want to know what I might be getting myself into cost-wise and if this fix really sorts it out for good. Cheers!

Hey there! Happy to give you an update about the costs and how things turned out. I just got my car back from the mechanic last week, and I paid 515 € to fix the faulty injection valve that was causing the mixture preparation error. Honestly, it was worth every penny because my M850i is running like a dream now! Let me tell you, the difference is night and day. No more jerking during acceleration, the idle is smooth as silk, and that annoying check engine light is finally off. The engine feels strong again, just like it should. It's such a relief after dealing with all those issues. I know the repair cost might seem steep, but considering the complexity of these engines and the specialized work involved, I'd say it's reasonable. Plus, it's way better than risking more expensive damage down the line. Since the fix, I haven't had a single problem, the car performs exactly like it should. Pro tip: keep an eye on your fuel quality and stick to regular maintenance schedules. It helps prevent these issues from coming back. Trust me, you won't regret getting this sorted properly!

Thanks so much for the detailed follow-up! Just wanted to give a quick update, I took your advice and found a mechanic who specializes in BMW engines. You were spot on about the injectors! Took my car in yesterday and they found two bad injectors plus some carbon buildup. The repair cost was a bit higher than yours at 780 €, but they did a complete fuel system cleaning too. The mechanic was super transparent, showed me the damaged parts, and explained everything clearly. Got the car back today and wow, what a difference! The engine purrs like new, no more jerking or rough idle. That annoying check engine light is finally gone. Such a relief to have this sorted properly instead of going around in circles with quick fixes. Really appreciate your help in pointing me in the right direction. Time to enjoy driving my 8 series again without worrying about every little noise. Thanks again for saving me from more headaches!