BMW 5 Diesel Cold Start & Power Issues, Help Needed

Hey there! I've got some experience with BMWs as I had a similar issue with my 2002 BMW 3 Series diesel (had a 320d before upgrading to a 330d). What you're describing sounds exactly like what I went through. My car had the same symptoms, hard cold starts, excessive fuel consumption, and power issues. Turns out, it was connected to a previous repair where the mechanic didn't properly reset the ECU after some work. Luckily, I didn't have to pay anything since it was the workshop's mistake. They just had to recalibrate the engine management system and clear the fault codes. Took about an hour and the car was running like new again. Could you share what engine variant you have and if you've had any recent work done on the car? Also, have you scanned for error codes? This info would help me give you more specific advice based on my experience.

Thanks for sharing that! My car's been pretty reliable until now, just had its service last month at 147479 KM. I think you might be onto something with the ECU stuff. I actually had some work done on the fuel system about three weeks ago, and that's roughly when these issues started. Haven't scanned for codes yet, but I'm planning to get that done tomorrow. Mine's the 2.5L diesel variant, and it's usually a solid engine. I'll definitely check with my mechanic about the ECU calibration, that could save me from some expensive repairs if it's just a reset issue like yours was. Thanks for pointing me in that direction!

Oh that's exactly what I thought when you mentioned the recent fuel system work! I'm honestly pretty relieved you brought that up because it's so similar to what happened with my 320d. The timing of your issues starting after that work is a massive red flag, just like what happened with mine. Listen, when I had the fuel system work done on my Beemer, they messed with the fuel pressure sensors, and the ECU just couldn't get its act together afterward. It's crazy how these modern engines need everything to be perfectly calibrated, right? Since you've got the 2.5L, it's even more sensitive to these things than my old 320d was. One thing I learned from my experience, make sure they do a proper ECU reset and adaptation procedure. My mechanic initially just cleared the codes, but that didn't solve it. They had to do a complete adaptation cycle for it to work properly again. Quick tip: before you head to the mechanic tomorrow, try to note down exactly when the problems occur, like if it's worse first thing in the morning or after the engine's been running for a while. This really helped my mechanic pinpoint the issue with mine. Keep us posted on what the scan shows. I've got a feeling it'll be something similar to what I dealt with!

Thanks everyone, especially for the detailed advice about the ECU reset and adaptation procedure! Just got back from the mechanic, and you guys won't believe it, the scan showed multiple sensor-related codes, all pointing to that fuel system work I had done. They found that the fuel pressure sensor wasn't properly calibrated after the last service, and the ECU was getting confused readings. The mechanic's doing a complete system reset and recalibration now. They're also running that adaptation cycle you mentioned, apparently, it's super important for these diesel engines to relearn everything properly. The best part? They're doing it under warranty since it's related to the previous work. Really appreciate all the help here, you saved me from panicking about potentially major engine problems! I'll update once I get the car back, but I'm feeling pretty optimistic now. Goes to show how important it is to get these modern engines properly reset after any work. Thanks again for sharing your experiences, definitely helped point me in the right direction!