BMW X7 Diesel: Cold Start Issues & Performance Problems

Hi there! I have some experience working on cars, and I actually faced something similar with my 2018 BMW X5 diesel last winter. Talk about timing, these issues can be really frustrating! I had almost identical symptoms on mine, and after taking it to my regular workshop, it turned out to be a faulty wiring connection to the fuel heater component. The mechanic found corroded terminals that were causing intermittent connection issues. The repair was pretty straightforward, they replaced the damaged wiring and connectors, which cost me 95 Euro. Since then, the car's been running perfectly, no more cold start issues or power problems. The X5 and X7 share quite a few components, so this might be worth checking out on yours too. Could you share your exact error code? Also, how long have you been experiencing these symptoms? This would help me give you more specific advice based on my experience.

Thanks for sharing your experience! I've got the same 2020 X7 diesel with 38668 KM on the clock. Just had my latest service done two weeks ago, and they didn't spot anything unusual. Your wiring issue suggestion makes a lot of sense, my symptoms are nearly identical. The error code I'm getting is P0380. Started noticing these issues about three weeks ago when temperatures dropped. Actually, the rough idle is most noticeable right after cold starts, and seems to smooth out once the engine warms up. The fuel consumption increase has been pretty noticeable, I'm using about 15-20% more than usual. Your fix sounds promising and way more affordable than what I was expecting. Think I'll get those connections checked out first before looking at more expensive repairs.

Hey again! Thanks for getting back with those details. Yeah, that P0380 code is definitely related to the glow plug system, which matches up perfectly with what I experienced. It's interesting that you mentioned it started with the temperature drop, that's exactly how mine began too. From my experience with the BMW, once the wiring was fixed, my fuel consumption dropped right back to normal within a tank or two. I remember being shocked at how much extra fuel I was burning through before the repair, sounds just like what you're dealing with. One thing I noticed with mine that might help you, check if your idle gets better after about 3-4 minutes of running. That was a dead giveaway for me that it was electrical rather than a mechanical issue. My mechanic mentioned that these problems often show up right after services too, as moving things around during maintenance can sometimes expose weak connections. With your mileage being similar to what mine was when I had the issue (I was at about 42000 KM), I'd definitely recommend getting those connections checked first. The fix isn't usually too complex, my car was in and out of the shop in about two hours. Let me know what you find out, I'm curious if it turns out to be the same issue!

Thanks so much for all the detailed info! You've given me a lot more confidence about what I'm dealing with. I just checked and yeah, the idle does improve after a few minutes of running, exactly like you described. Funny how these things follow such similar patterns. I've already called my mechanic and booked it in for tomorrow morning. Mentioned the wiring issue you experienced and the P0380 code, and he agreed it sounds like a solid lead. Really hoping it's just the connections like yours was, would be great to get this sorted quickly and cheaply. Thanks again for sharing your experience, it's been super helpful. I'll definitely update the thread once I get the diagnosis. These kinds of real-world solutions are exactly what I was looking for when I posted. Really appreciate you taking the time to walk me through your similar situation!