BMW 8 Cold Start Problems, Bad Injector Symptoms?

Hey there! I had a very similar issue with my 2016 BMW 7 Series last winter. I've got some experience working on cars, but nothing too advanced. My car was showing pretty much the same symptoms as yours, rough cold starts, high fuel consumption, and even some misfiring. After struggling with it for a week, I took it to my regular workshop. Turned out one of the fuel injectors was defective and needed replacement. The repair cost me about 515 Euro, including parts and labor. Since then, the car's been running smooth as butter. Before I can share more specific details, could you tell me which engine variant you're running in your 8 Series? Also, have you noticed any check engine lights or specific error codes? This would help me give you more relevant advice based on my experience. The repair was totally worth it though, saved me from potential bigger issues down the line.

Thanks for sharing your experience! My car has covered 70832 KM and had its last service about 2 months ago. The check engine light hasn't come on yet, but I'm running the 4.4L V8 gasoline engine. I'm definitely getting those same symptoms you mentioned, the rough idle and higher fuel consumption are particularly noticeable in the morning. Good to know it was the injector in your case. That repair cost seems reasonable considering the alternative of letting it get worse. Did you notice any performance improvements after the fix, especially during cold starts? My fuel economy has really taken a hit lately, so I'm hoping it might be something similar and relatively straightforward to fix.

Hey again! Yeah, I totally understand what you're going through. With my 7 Series having the 4.4L V8 as well, I can definitely make a good comparison. After getting that injector replaced, the difference was like night and day! The engine started purring right from cold starts, no more of that rough running or excessive fuel drinking. My fuel economy improved by about 15-20% once everything was sorted. The morning starts became way smoother too, none of that hesitation or rough idle you're experiencing. Since you mentioned your car was serviced recently, did they do any fuel system cleaning? Mine actually had some carbon buildup issues along with the faulty injector. The mechanic recommended a fuel system cleanup while they were at it, and I think that helped with the overall performance too. Just a heads up though, if it is an injector issue like mine was, better get it checked sooner rather than later. I learned the hard way that leaving it too long can cause more problems. The repair cost I mentioned earlier was actually pretty reasonable considering what could've happened if I'd kept putting it off. Let me know what you decide to do. Always happy to share more details about my experience if you need them!

Thanks so much for the detailed follow-up! That's really encouraging to hear about the improvements you saw after the fix, especially with us having the same engine. I hadn't thought about the carbon buildup angle, but it makes total sense. No, they didn't do a fuel system cleaning during my last service, they just did the regular maintenance items. I'm going to book it in with my mechanic next week. You've convinced me it's better to deal with this now rather than wait for it to potentially get worse. The fuel savings alone sound worth it, not to mention avoiding any bigger issues down the line. That 15-20% improvement in fuel economy you mentioned would be amazing right now. Really appreciate you taking the time to share your experience. It's definitely helped me understand what I might be dealing with. I'll probably get them to look at doing that fuel system cleanup too while they're at it. I'll let you know how it turns out!