BMW X3 Vacuum Leak? CEL, Stalling & Poor Performance

Hey there! I have some experience working on cars, and I actually dealt with something very similar on my 2020 BMW X1. Based on those symptoms you described, especially the hissing and poor fuel economy, it really sounds like what I went through. Mine turned out to be a cracked intake hose that was causing a vacuum leak. The mechanic spotted it during inspection, it had a small tear that was letting in unmetered air. Got it replaced for about 100 Euro and all those issues disappeared right away, no more stalling, better fuel economy, and the CEL cleared up. Can you hear where the hissing is coming from specifically? Also, are you getting any specific error codes with that CEL? Would help confirm if we're dealing with the same thing here. By the way, I had this fixed at my regular workshop, and theyaged to get it done in about an hour. Pretty straightforward fix once they identified the problem.

Thanks for sharing your experience! My X3 has about 33993 KM on the clock and was just serviced last month, so this issue caught me off guard. The hissing seems to be coming from the front right side of the engine bay, and I'm getting P0171 code (system too lean). Considering our similar symptoms, I'll definitely have my mechanic check the intake hoses first. That repair cost sounds way better than what I was worried about! Did you use OEM parts for the replacement?

Hey again! Yes, on my X1 I did go with OEM parts. Even though aftermarket options were cheaper, I didn't want to risk having the same issue pop up again. The OEM hose has been solid for about 15 months now with no issues. One thing I forgot to mention in my first reply, when my mechanic was checking the intake system, they also found that the clamps had gotten a bit loose over time. They tightened those up while they were in there, no extra charge. Might be worth having yours checked too, especially since you mentioned the recent service. That P0171 code is exactly what I got too! And the location of the hissing matches up perfectly with my experience. Since your mileage is pretty close to what mine was when this happened (I was at around 37000 KM), it's looking more and more like the same issue. Just make sure your mechanic does a thorough smoke test to pinpoint the exact location of the leak. In my case, the tear was pretty small and could have been easily missed without proper testing. Better to catch everything while they're already working on it. Let me know how it turns out!

Thanks so much for all the detailed info! You've definitely convinced me to check the intake system and go with OEM parts. I just called my mechanic and scheduled an appointment for tomorrow morning. They'll do the smoke test you mentioned to find the exact location of the leak. Makes total sense about checking the clamps too, I'll make sure to bring that up. Really glad I asked here because that repair cost is such a relief compared to what I was imagining. Being a BMW owner, I was bracing myself for much worse! I'll update the thread once I get it fixed in case anyone else runs into similar issues with their X3. Thanks again for taking the time to share your experience, it's been super helpful!