BMW X7 Diesel Rough Running: QDC Issues or Something Else?

Hey there! I can relate, I had a very similar issue with my 2018 BMW X5 diesel last year. I have some experience working on cars, but honestly, injector problems are beyond my comfort zone. When my X5 started acting up with similar symptoms (rough idle, misfires, CEL), I first thought it might be something simpler. My trusted workshop diagnosed it as a faulty injector on cylinder 3. They had to replace the injection valve, and yeah, it set me back about 515 Euro, but the car's been running like a dream since. Before suggesting anything specific for your X7, could you let me know: How many miles/kilometers on the clock? Does it happen more when the engine is cold or warm? Have you noticed any excessive smoke from the exhaust? Side note, my drives a BMW X3, and these diesel engines are pretty similar across the range, so I've learned a bit about their common issues. Let me know those details, and I might be able to share more relevant info from my experience.

Thanks for your response! I'm at 43754 KM and just had my service done last month. To answer your questions, it happens regardless of engine temperature, but it's definitely more noticeable when cold. Haven't noticed any unusual smoke from the exhaust though. Your injector experience sounds pretty similar to what I'm dealing with. Did you notice any specific symptoms right before the injector completely failed? Just trying to figure out if I need to get this sorted immediately or if I can drive it for another week until my preferred workshop has an opening.

Hey again! Happy to share more about my X5 experience since it's really similar to what you're going through. Looking at your mileage and symptoms, it's eerily similar to what happened with mine. Right before my injector completely gave up, I noticed the roughness got progressively worse over about two weeks, especially during cold starts. My mistake was waiting too long, ended up having to get towed when the engine finally went into limp mode during my commute. I'd strongly suggest not waiting that week if you can help it. While I understand wanting to go to your preferred workshop, these injection issues can escalate pretty quickly. In my case, the rough running and misfires were basically the engine's way of waving a red flag. When I ignored those warnings, I ended up paying more because the faulty injector started affecting other components. One thing I learned from my experience, modern diesel engines are super sensitive to injection problems. The quantity drift compensation you mentioned in your first post could definitely be related, but in my case (and quite often), it was the injector itself that needed replacing. Trust me, getting stranded isn't fun. Maybe see if your preferred workshop can squeeze you in sooner? Or consider a temporary alternative? Better safe than sorry with these engines.

Thanks so much for the detailed advice, really appreciate you sharing your experience! You've definitely convinced me not to wait. Just called my workshop and explained the situation, and they're actually able to fit me in tomorrow morning. Better to deal with it now than risk getting stranded like you did. The similarities between our cases are pretty striking, so I'm betting it's also injector-related. Will update the thread once I know what's actually wrong with it. Really grateful for your help, it's exactly the kind of real-world experience I was hoping to hear about. Thanks again for taking the time to share all this!