M3 Rough Running + High Fuel Use: Common Causes Revealed

Hey there! I've got some experience with cars (some experience level) and had a very similar issue with my 2021 BMW M4. Like yours, mine started running really rough with poor acceleration and high fuel consumption. Turned out one of my injectors was faulty, causing uneven fuel delivery. Took it to my regular workshop and they diagnosed it through computer testing. They replaced the defective injector, which set me back about 515 Euro, but it fixed the problem completely. The car runs smooth as silk now. Since your symptoms sound identical, I'd recommend getting it checked ASAP to prevent any engine damage. Could you share your mileage and if you've noticed any specific conditions when the symptoms get worse (like cold starts or high RPMs)? Also, have you scanned the error codes? This info would help determine if we're dealing with the same issue.

Hey, thanks for sharing your experience! My M3 has 46027 KM and just had its latest service last month. Mine definitely gets worse during cold starts and when pushing it above 4000 RPM. Haven't scanned the codes yet but planning to do that tomorrow. Really hoping it's just an injector like in your case, that sounds like a manageable fix. The symptoms you described match mine exactly, especially that rough running and high fuel consumption. Did you notice any weird smells from the exhaust when you had the issue?

Hey again! Yeah, now that you mention exhaust smells, I definitely noticed a strong fuel smell from my M4 when the injector was acting up, especially during cold starts. It was that typical rich fuel smell, you know? That's actually one of the things that first caught my attention before all the other symptoms got worse. Looking at your mileage and the symptoms, particularly the cold start issues and problems above 4000 RPM, it's sounding more and more like what I dealt with. The fact that it's getting worse when pushing it harder is exactly what happened with mine, the faulty injector couldn't keep up with the demand at higher RPMs. Getting those codes scanned tomorrow is definitely the right move. When my mechanic pulled the codes on my M4, it showed a clear fuel system issue. Just make sure you don't push the car too hard until you get it checked out. I learned that the hard way, drove it a bit too long with the symptoms and ended up with carbon buildup that needed cleaning too. Keep me posted on what those codes show up. If it's the same issue, at least you know it's a straightforward fix. The peace of mind after getting it sorted was worth every penny!

Thanks for all that detailed info, especially about the fuel smell! Actually, now that you mention it, I've definitely been noticing that strong fuel odor, particularly when I first start it up in the morning. It's good to know I'm not just imagining things. I really appreciate the heads up about not pushing it too hard. I was tempted to do some highway runs this weekend, but I'll hold off until I get those codes read. Don't want to risk any extra carbon buildup like you experienced. That would just add unnecessary costs to the repair. Will definitely scan it first thing tomorrow and let you know what I find. Fingers crossed it's just an injector issue like yours was. The repair cost you mentioned seems reasonable compared to what I was worried it might be. Thanks again for sharing your experience, it's really helpful to hear from someone who's been through the same thing!