BMW 4 Diesel Cold Start Nightmare, Injector Issues?

Hey there! I had a similar issue with my 2018 BMW 3 diesel earlier this year. I have some experience working on cars, but I left this one to the professionals since injection systems are pretty complex. The symptoms you're describing sound exactly like what I dealt with, rough cold starts, multiple attempts needed, and terrible fuel consumption. Turned out one of my injectors was faulty. Took it to my regular workshop, and they diagnosed it using their diagnostic computer. Had to replace the defective injector, which set me back about 515 Euro, but the car's been running perfectly since then. Before I can share more specific details, could you tell me your exact engine variant and mileage? Also, are you getting any warning lights on the dashboard? This would help me give you more relevant advice based on my experience.

Thanks for sharing your experience! Mine's at 118292 KM and just had its last service 2 months ago. No warning lights showing up at the moment, which makes it a bit tricky to diagnose. I'm leaning towards taking it to a specialist workshop too, especially after hearing about your similar situation. Did your mechanic mention how they were able to pinpoint which injector was the culprit? Just want to be prepared when I take it in.

Hey again! Yeah, I totally understand wanting to know more about the diagnostic process, I was curious about that too when I had my issue. In my case, the mechanic used their advanced diagnostic tool that could read the injection timing and spray patterns of each injector. They basically ran specific tests while monitoring the fuel pressure and return rates from each injector. What was really interesting is that they found my faulty injector wasn't spraying fuel consistently during the cold start phase, it was kind of sporadic, which explains the rough running. The diagnostic computer showed irregular fuel delivery patterns compared to the other injectors. They even showed me the readings, though honestly, it looked like gibberish to me! Since your mileage is pretty close to what mine was (I was at around 125,000 KM when it happened), it makes sense you might be facing similar issues. The fact that you're not getting any warning lights is exactly what happened with mine too, these problems can sometimes fly under the radar of the car's warning system. One thing I forgot to mention earlier, before getting it fixed, I noticed my car also had a slight hesitation when accelerating from cold. Did you notice anything like that? Just curious if you're experiencing the same patterns I did. Let me know how it goes when you take it to the workshop!

Thanks for that detailed explanation! Yes, actually I have noticed that hesitation during acceleration when cold, I just didn't connect it to the same issue until you mentioned it. It's really helpful to know about the diagnostic process they used with your car. I've booked mine in for next week at a BMW specialist workshop, and knowing about the injection timing tests gives me something specific to discuss with them. The similar mileage and symptoms make me pretty confident we're dealing with the same problem. I was worried it might be something more serious or expensive, but an injector replacement sounds manageable. I'll update once I get it checked out, might help someone else with similar issues down the line. Really appreciate you taking the time to share your experience in such detail. It's definitely made me feel better about getting this sorted!