BMW 4 Series Engine Issues: Valve Train Noise Concerns

Hey there! Yeah, I can totally relate. I had a very similar issue with my 2020 BMW 5 Series diesel last year. I've got some experience working on cars, but this one had me stumped at first. Mine started exactly the same way, rough running, check engine light, weird metallic sounds, and the fuel consumption went through the roof. After taking it to my trusted workshop, it turned out to be a faulty crankshaft position sensor. The whole thing, including labor and parts, set me back about 340 Euro. Since the fix, the car's been running perfectly. Could definitely be the same issue on your 4 Series, but I'd need to know: What's the exact mileage on your car? Are you getting any specific error codes? Does the problem get worse after the engine warms up? Let me know these details and I might be able to help more specifically!

Thanks for your response! My car has 162008 KM on the clock and just had its service last month. You might be onto something with the crankshaft position sensor theory. I'm getting error code P0016 mainly, and yes, the noise actually gets a bit better after warm-up, but the performance issues persist throughout. The metallic noise is really similar to what you described. I was a bit hesitant about the sensor being the culprit since I initially thought it was something more serious with the timing chain. The price you mentioned for the repair seems much more manageable than what I was mentally preparing for! Did you notice any warning signs before your sensor completely failed? I'm wondering if I should get this looked at immediately or if I can drive it for another week until my preferred mechanic has an opening.

Hey again! Glad I could help earlier. Yeah, that P0016 code definitely rings a bell, it's exactly what I got with my 5 Series. Looking at your mileage (162008 KM), it's actually pretty similar to when mine started acting up. You know what? I did notice some warning signs before it completely went south. Started with occasional hesitation during acceleration, especially in the mornings. The metallic noise came and went for about two weeks before it became constant. But here's the thing, I made the mistake of driving it longer than I should have, and it ended up causing some additional sensor issues that bumped up my repair bill a bit. From my experience, I wouldn't recommend waiting that week. The risk isn't worth it. When mine went completely bad during driving, it was pretty scary, sudden power loss on the highway isn't fun at all. Plus, if you keep driving it, you might end up with additional problems like I did. Quick tip though, if you absolutely must drive it, try to avoid heavy acceleration and keep the RPMs moderate. But honestly, I'd get it checked out ASAP. Better safe than sorry with these sensor issues, especially since they can cascade into bigger problems.

Thanks so much for the detailed advice, especially about your experience with letting it go too long. That's exactly what I needed to hear. You've convinced me not to wait on this. I just called my mechanic and explained the situation, and he's actually managed to squeeze me in tomorrow morning. The part about sudden power loss on the highway really hit home, definitely not something I want to risk! I'll take your advice and drive it very gently on my way to the shop tomorrow. Really appreciate you taking the time to share your experience. This has helped put my mind at ease about it likely being the sensor rather than a major timing chain issue. I'll update this thread once I get the diagnosis, might help someone else with similar symptoms in the future. Thanks again for all your help!