BMW 6 Diesel Cold Start Issues, Power Loss & CEL Help

I have some experience working on cars and faced a similar issue with my 2021 BMW 4 Series diesel. Had the exact same symptoms you're describing, sluggish cold starts, poor performance, and higher fuel consumption. Turned out the issue was connected to a previous repair where the fuel injectors weren't properly calibrated after replacement. Took it to my regular workshop and they discovered the calibration error during diagnostics. Since it was their mistake from the previous work, they fixed it at no cost. After proper calibration, the car runs perfectly again. What's your current mileage and maintenance history? Have you had any recent work done on the fuel system? This info would help narrow down if you're dealing with the same problem. BTW, if you need a reliable workshop recommendation that knows BMWs well, let me know. Proper diagnostics is crucial with these engines.

Thanks for sharing your experience! My car has 158485 KM on the clock, and it's been regularly serviced, with the latest service done just 2 months ago. Actually, no recent work has been done on the fuel system, and I haven't had any major repairs so far. Your injector calibration issue sounds interesting, I'll definitely have that checked. Did your car also show any specific error codes when you had this problem? Just trying to compare notes before I take it to a mechanic.

Hey there again! Thanks for the additional info about your car. Yeah, when I had this issue, my BMW actually threw error code P0263 (Cylinder 1 Contribution/Balance fault) and P0087 (Fuel Rail/System Pressure Too Low). These codes were what helped the mechanics identify the calibration issue with my injectors. Since you mentioned your car hasn't had any fuel system work done, it might be worth checking the fuel pressure sensor and the high-pressure fuel pump too. These parts can wear out over time, especially with that kind of mileage. When my injectors weren't properly calibrated, the fuel pressure would fluctuate a lot, causing those cold start issues we both experienced. One thing I noticed before taking it to the shop, the engine would make this slight rattling noise during cold starts, did you notice anything like that? Also, my fuel consumption went up by about 15-20% before I got it fixed. Are you seeing similar increases? I'd definitely recommend getting those error codes read first. Could save you some time and money by pointing directly to the issue. Let me know what you find out, curious to see if it's the same problem I had.

Really appreciate all this detailed info! Yes, actually I am getting a similar rattling noise during cold starts, and I've noticed about a 20% increase in fuel consumption too, pretty much exactly what you described. I'll definitely get those error codes checked first thing tomorrow. I've got a code reader at home, so I'll check if I'm getting the same P0263 and P0087 codes you mentioned. You've given me a solid starting point with the injector calibration, fuel pressure sensor, and high-pressure fuel pump to investigate. Makes total sense given my mileage. I've got a much better idea of what to discuss with the mechanic now rather than going in blind. I'll make sure to mention these specific issues you've had. Thanks again for all the help, you've saved me a lot of guesswork!