BMW 6 Diesel: Multiple Issues Point to Boost Sensor

Hey there! I have some experience with BMWs, having owned a 2013 BMW 5 series diesel and currently driving a 7 series. Your symptoms sound really similar to what I dealt with on my old 5 series. After the same issues you described, especially that annoying whistling and power loss, I took it to my regular workshop. Turned out it was indeed a faulty boost pressure sensor, specifically a loose connection in the wiring harness to the sensor. The fix was pretty straightforward, they replaced the wiring and connections, which cost me about 95 Euro. Car's been running perfectly since then. Before I can give you more specific advice, could you share: How many miles/kilometers are on your car? When did these symptoms first appear? Have you had any recent work done on the engine? Let me know these details and I might be able to help further!

Thanks for the detailed response! I'm at 72936 KM and just had my service last month. The symptoms actually started about two weeks after the service. Interesting that you had similar issues with your 5 series. The whistling sound is driving me crazy, especially during acceleration. I'm hoping it's just the sensor like in your case and not something more serious. Did you notice any specific conditions when the symptoms got worse? Like cold starts or high speeds?

Hey again! Thanks for the follow-up. Yeah, those details actually sound very familiar, especially the timing after the service. With my 5 series, I noticed the symptoms were definitely worse during cold starts, and the whistling was most noticeable when accelerating between 2000-3000 RPM. Since you mentioned it started after your service, I'd actually suggest checking if they might have accidentally disturbed some connections while working on the car. That's exactly what happened in my case, turned out the technician had inadvertently knocked a connector loose while doing routine maintenance. The cold start issues were particularly bad for me, the car would struggle for about 30 seconds before settling into a normal idle. And yeah, the whistling noise would get really intense during highway merging or overtaking. Sound familiar? Just a heads up, if it is the boost pressure sensor like mine was, don't wait too long to get it fixed. I tried to "live with it" for a few weeks and ended up using way more fuel than necessary. Plus, running with incorrect boost pressure readings isn't great for the engine in the long run. Quick question, have you noticed if the symptoms are any different when it's raining or particularly humid? My car used to act up more in wet weather, which was another clue that pointed to an electrical connection issue rather than a mechanical problem.

Thanks so much for sharing those extra details, you're describing my symptoms exactly! Yes, the cold starts are awful, and I get that same intense whistling between 2000-3000 RPM. Come to think of it, the car does seem to struggle more on rainy days, which I hadn't even connected until you mentioned it. I'll definitely get it checked out right away now. That loose connector theory makes total sense since it started right after the service. Really appreciate your help, you've saved me from worrying it might be something major like the turbo. I'll call my mechanic first thing tomorrow and specifically ask them to check the boost pressure sensor connections. Will let you know how it turns out. Thanks again for taking the time to help me troubleshoot this!