BMW M4 Owner Reports Misfire and Performance Issues

Hey there! I had similar symptoms with my 2018 BMW M3 last year, and I have some experience working on cars as a hobby mechanic. Those symptoms match what I dealt with, turned out to be a faulty fuel injector. I was getting the same issues: poor acceleration, rough idle, and that dreaded check engine light. My trusted workshop diagnosed it as a defective injection valve, and they had to replace it. The whole thing set me back about 515 Euro, but it was worth every penny as it completely solved the problem. The car's been running smooth as silk since then. Before you proceed, could you share: Have you scanned for error codes? Is there any unusual smoke from the exhaust? Does it happen more when the engine is cold or warm? This info would help me give you more specific advice based on my experience with the M3 and other BMWs.

Thanks for the detailed response! Just had my car serviced two weeks ago at 160820 KM, and these issues started showing up right after. I did scan for codes and got P0301 and P0302 pointing to cylinder misfires. No unusual smoke, but the problem seems worse when the engine's cold, especially in the morning. The timing seems suspicious since it started right after the service. Makes me wonder if something got knocked loose during maintenance. Your fuel injector experience sounds pretty similar to what I'm dealing with. Might need to get that checked out. Really hoping it won't need all injectors replaced, as that would be a much bigger bill than what you paid.

Hey again! those codes you mentioned (P0301 and P0302) really got my attention because that's exactly what my M3 was throwing before I got it fixed. And the fact that it started right after your service? That's definitely suspicious. When my car was acting up, I initially thought all injectors needed replacement too, I was sweating bullets thinking about the cost! But thankfully, it turned out to be just one bad injector. Though I gotta say, since you mentioned it's happening right after service, I'd also check if the spark plugs and ignition coils were properly reinstalled. My mechanic once told me these can sometimes get loose during routine maintenance. In my case, the cold start symptoms were a dead giveaway for the injector issue. The car would shake like crazy for the first few minutes, just like what you're describing. I'd definitely suggest getting it back to the shop that did your service, they should at least check if anything was left loose during maintenance. If they're decent, they might even cover it under service warranty if it turns out they messed something up. Keep me posted on what you find out, really curious if your issue mirrors what happened with my M3. These performance BMWs can be finicky sometimes, but they're worth the hassle when they're running right!

Thanks so much for sharing your experience! You've actually made me feel a lot better about this whole situation. I just called the service center and they've agreed to take a look tomorrow, especially since it started right after they worked on it. They seemed particularly interested when I mentioned the cold start symptoms and the specific error codes matching your old M3's issue. You know what? I was really stressing about potentially needing a complete injector overhaul, but hearing that yours was fixed with just one replacement is reassuring. I'll definitely have them check the spark plugs and ignition coils too, that's a great point about them possibly being loose after service. I'll keep this thread updated once I get the diagnosis. Really appreciate you taking the time to share your experience in such detail. These cars can definitely be demanding sometimes, but like you said, they're absolutely worth it when everything's running right. Fingers crossed it's something simple like in your case!