BMW X6 Diesel Power Loss: Intake Manifold Warning Signs

Hey there! I had nearly identical symptoms on my BMW X5 35d (2015) last summer. The hissing sound and power loss are telltale signs of a faulty intake manifold control. From my experience at the shop, they found that the actuator for the manifold flaps had failed, causing them to stick in one position. This prevented proper air distribution in the manifold, leading to the rough running and increased fuel consumption you're describing. The repair involved replacing the entire intake manifold assembly since the actuator is integrated into it. It was a fairly serious job, took the technicians about 6 hours to complete. The engine needs to be partially disassembled to access the manifold properly. Don't wait too long to get it fixed. Running the engine with malfunctioning intake flaps can potentially cause more damage down the line. Based on your symptoms, I'd say it's worth getting it checked by a certified BMW technician rather than a general mechanic. Not something you can really DIY either, it needs proper diagnostic equipment to verify the flap positions and calibrate the new assembly.

Thanks for sharing your experience, sounds exactly like what I'm dealing with! That's really helpful insight about the actuator being integrated into the manifold assembly. I think I'll definitely get it checked at a certified shop soon. Do you remember roughly how much you ended up paying for the whole repair? Also, has everything been running smoothly since the fix, or have you had any other related issues pop up? Just trying to get an idea of what I'm in for.

Hey again! Yep, I can give you a full update on my X5 situation. After getting it fixed at the certified shop, it's been running like a dream, no more hissing, power loss, or any of those annoying symptoms. The repair bill came to 465 € for replacing the faulty switch intake manifold control, and honestly, it was worth every penny. It's been about 8 months now since the repair, and I haven't had a single issue related to the intake manifold. The fuel consumption went back to normal, and the engine's performing just like it should. The hissing sound completely disappeared, which was such a relief! One thing I really appreciate now is how smooth the acceleration is compared to when the flaps were acting up. If you're hesitating about getting it done, don't, it's definitely worth fixing before it causes any additional problems. And based on my experience, going with a certified shop was the right call. They knew exactly what they were dealing with and got it sorted properly the first time. Just make sure they give you a proper warranty on the work. Mine came with a 2-year guarantee on the parts and labor, which gave me good peace of mind.

Thanks so much for all the details! I actually just got back from the certified shop today and you won't believe it, it was exactly what you described. The mechanic confirmed the faulty intake manifold control and I went ahead with the repair. Ended up paying a bit more than you did, but the difference wasn't too bad. They really knew their stuff and walked me through everything they were doing. Got a similar warranty deal too, which made me feel much better about the investment. The drive home was like night and day! No more hissing, the power's back, and it's running super smooth again. Guess I should've gone to them first instead of wasting time with that other mechanic. Really glad I asked here and got your advice, saved me from potentially making things worse by waiting too long. Thanks again for helping me out with this. It's such a relief to have it sorted properly now!