BMW M4 Fuel System Issues: Symptoms and Solutions

Hi there! I've had some experience working on cars, and this sounds very similar to what I faced with my 2017 BMW M2 a while back. The symptoms you're describing ring a bell, my car showed the exact same issues. After taking it to my trusted workshop, it turned out to be a loose connection in the wiring harness to the fuel pump sensor. The repair was straightforward, they fixed the faulty connection and replaced a damaged plug, costing me 95 Euro in total. The problem never came back after that, and my car has been running smoothly since then. I've also owned an M3 before, and these models can be sensitive to electrical issues. Before I can help more specifically, could you share: Have you scanned for exact error codes? When exactly did these symptoms start? Does it happen more when the engine is cold or warm? Feel free to ask if you need more details about my experience!

Hey, thanks for sharing your experience! My M4 has 104360 KM on the clock, and I've kept up with all scheduled maintenance. Just got the error codes scanned, showing P0171 and P0174 (system too lean). The symptoms started about a week ago, and it's definitely worse when the engine is cold, especially in the morning. After warming up, it runs a bit better but still not great. I'll definitely check the wiring connections you mentioned, that's a much better scenario than a complete fuel pump replacement! Did you notice any specific sounds or behavior when starting the car in your case? Mine makes a slight whining noise before it finally catches. Thanks again for the detailed response, really helpful to hear from someone who's dealt with something similar!

Hey again! Thanks for those details about your M4. You know what's interesting, when my M2 had these issues, I also heard that exact same whining noise you're describing! However, in my case, after they fixed that wiring connection I mentioned, we actually discovered the main culprit was a clogged fuel filter. The lean codes you're getting (P0171 and P0174) are super similar to what I dealt with. My car had about 98000 KM when this happened, and those same codes popped up. The whining noise is really telling, it's that classic sound of a fuel system struggling to maintain proper pressure. Quick question, have you checked your fuel filter maintenance history? In my case, it had never been changed, and it turned out it was so clogged it was restricting fuel flow. Once I got both the wiring fixed AND a new fuel filter installed, all those symptoms disappeared completely. Total repair ended up being a bit more than just the wiring issue I mentioned before, around 280 for both fixes, but way better than replacing the whole fuel pump. The car's been running like a dream for the past 18 months since then. Let me know if you want more specific details about the repair process, happy to share what I learned from my experience!

Thanks so much for the additional info, that's really eye-opening about the fuel filter! Actually, I just checked my maintenance records and realized I've never had the fuel filter changed either. That could definitely explain a lot, especially since our cars had similar mileage when these issues came up. The total repair cost you mentioned sounds much more reasonable than what I was worried about spending on a new fuel pump. I'm going to call my mechanic tomorrow and specifically ask them to check both the wiring connections and the fuel filter. It makes total sense that a clogged filter could cause these lean conditions. I really appreciate you taking the time to share your experience in such detail. This has given me a much clearer direction on what to look into. I'll definitely update once I get it sorted out!