BMW 6 Diesel Problems: MPF Sensor or Something Else?

Hey! Had a similar issue with my '05 BMW 5 diesel. The symptoms you're describing sound exactly like what I experienced. Initially thought it was the sensor too, but my mechanic found a significant vacuum leak. The diagnostic showed multiple error codes, and the power loss was quite noticeable. Took it to my regular workshop last year, they did a thorough check and found cracks in some vacuum lines. Total bill came to 235 Euro for parts and labor, but the car's been running perfectly since. The fuel consumption went back to normal too. Which engine variant does your 6 series have? Also, are you getting any specific error codes? This could help pinpoint whether you're dealing with the same issue. These BMWs can be tricky, but most vacuum leaks are fixable without breaking the bank.

Hi, appreciate your detailed response! My car's got 88934 KM on the clock, and you might be onto something with the vacuum leak theory. After my last service, the mechanic mentioned the vacuum lines were showing some wear. My symptoms do match what you described. I'm getting error code P0299, which apparently relates to boost pressure. Was thinking about taking it to the shop this week, your repair costs sound much more reasonable than what I was dreading! Just wondering, how long did the whole repair process take for you? And did you notice any warning signs before the power loss kicked in? The engine's a bit of a thirsty one anyway, but lately it's been way worse than usual. I'll definitely get those vacuum lines checked first before jumping to sensor replacements.

Hey again! Yeah, I remember my repair situation quite well. The whole thing took about 4-5 hours at the workshop. My mechanic actually found multiple hairline cracks in the vacuum lines, they weren't obvious at first glance. Looking back, there were some early warning signs I ignored. About a month before the power loss became really noticeable, I was getting this slight whistling sound under acceleration. Also, the idle was a bit rougher than usual, especially when the engine was cold. Didn't think much of it at the time, but those were definitely red flags. That P0299 code you're getting? That's exactly what showed up on mine too. Given your mileage and symptoms, I'd bet good money you're dealing with the same vacuum leak issue. These BMWs are known for it, the lines can get brittle over time, especially if they're the original ones. The fuel consumption on mine went from bad to worse really quickly. Was burning through about 15-20% more fuel before I got it fixed. Once they replaced those lines though, it was like having a new car again. The power came back immediately, and the engine light cleared up. Definitely get it checked soon though, driving with a vacuum leak isn't great for the engine long term. Let me know how it goes!

Thanks so much for all this detailed info! You've really put my mind at ease. That whistling sound you mentioned, I've actually been hearing something similar for the past few weeks but didn't connect the dots until now. My idle's been a bit rough too, especially in the mornings. I've just booked it in at the workshop for tomorrow morning. Called them and described everything, including what you've shared about your experience. They seemed to agree that vacuum lines are the likely culprit. Said they'll do a pressure test first to confirm. Really relieved it might just be the vacuum lines rather than something more serious. 4-5 hours doesn't sound too bad either, I can probably get it sorted during my work day. I'll definitely stop putting it off now, especially knowing it could get worse for the engine if I keep driving it like this. I'll update the thread once I get it back from the shop. Thanks again for sharing your experience, it's been super helpful!