BMW X4 Diesel: Boost Pressure Woes and Warning Lights

Hey there! Got some experience with BMWs as I dealt with very similar symptoms on my 2018 BMW X3 diesel last year. I also have a X1 in the garage, so I'm fairly familiar with these engines (some experience level). That whistling sound plus power loss rings a bell. Mine turned out to be a faulty wastegate valve. The turbo wasn't regulating boost pressure properly, which explains both the weird sounds and the poor performance. Took it to my trusted workshop, and they diagnosed it after thorough testing. The fix wasn't cheap, set me back about 860 Euro, but the car's been running like new since. To help you better, could you share: Current mileage? When did the symptoms first appear? Any black smoke from exhaust? Does the problem get worse when the engine's hot? These details would help confirm if you're facing the same issue. The symptoms you're describing are pretty spot-on with what I experienced though.

Thanks for sharing your experience! I've got 108602 KM on mine, and just had the service done last month. No black smoke from the exhaust, but the symptoms started about a week ago and definitely get worse when the engine warms up. Your wastegate valve situation sounds very similar to what I'm experiencing. Really helpful to know about the potential costs too, at least I can mentally prepare for the hit to my wallet. Did you notice any warning codes before getting it checked out? I'm tempted to get a diagnostic reader before heading to the shop.

Hey again! Yeah, I totally get why you're asking about diagnostic codes, I actually did get a few before taking mine in. Got P0299 and P0234 codes when I checked with my basic OBD reader. But honestly, the reader didn't tell me much more than what I already suspected from the symptoms. Just to add to my previous response about the wastegate valve, mine started acting up around 95000 KM, so your mileage and symptoms tracking worse after warm-up really do sound familiar. What's interesting is that before I got it fixed, I tried driving it really gently for a few days thinking it might help, but the problems just kept getting worse. One thing I didn't mention before, after the repair, my fuel consumption dropped back to normal within one tank. Was pretty satisfying to see that! The whistling noise disappeared completely too. If you're concerned about costs, you might want to check if you've got any warranty coverage left. I didn't on mine, hence the full payment, but some newer models have extended powertrain warranties that might cover this. Definitely get it checked soon though, running with a faulty wastegate can cause more expensive problems down the line. I learned that the hard way with my old X1!

Thanks so much for all the detailed info! This has been super helpful. I'll definitely get it checked out ASAP, you've convinced me not to wait around, especially hearing about potential further damage. I actually just checked, and my warranty expired two months ago (just my luck!). I've gone ahead and ordered an OBD reader online, should arrive tomorrow. At least I can confirm if I'm getting the same codes you mentioned before taking it to the shop. It's oddly reassuring to hear someone else had the exact same symptoms, especially with the whole getting worse after warm-up thing. That was really starting to worry me. Will probably book it in next week with my local BMW specialist. Rather deal with a hit to my wallet now than risk bigger problems later. Really appreciate you taking the time to share all this info, definitely helped me understand what I might be dealing with. I'll try to remember to update here once I get it sorted, might help someone else down the line with similar issues!

Boost pressure control - boost pressure too low

(Translated from German)

Check for any loose or damaged hoses in the turbo system, as a leak could cause low boost pressure and the symptoms you're experiencing. If you find any issues, have them repaired promptly. Let us know how it goes or if you have further questions!