BMW M4 Running Rich: Power Loss & Fuel Efficiency Issues

Hey there! I had nearly identical issues with my 2020 BMW M3 last winter. The symptoms you're describing match exactly what I experienced, rough idle, power loss, excessive fuel consumption, and that annoying check engine light. Turned out to be a faulty fuel injector. One of them was stuck partially open, which explained the rich fuel mixture. The jerky acceleration happened because the cylinder wasn't firing properly. In my case, two injectors needed replacement. It was definitely a serious issue that required immediate attention, driving with faulty injectors can damage your catalytic converter and engine in the long run. My garage diagnosed it pretty quickly with their diagnostic tool, and I needed to leave the car with them for a day and a half for the repair. Given you're still under warranty with the 2023 M4, I'd strongly suggest taking it to the dealer. This isn't something you want to risk with a non-specialist garage. Hope this helps.

Thanks for sharing your experience, this is exactly what I needed to hear! I was worried it might be something more serious, but your fuel injector story makes a lot of sense given the symptoms. By the way, do you remember roughly how much you ended up paying for the repair? Also, has everything been running smoothly since then, or did you run into any other issues? I'm thinking I'll get it checked out this week before it gets any worse. Like you said, don't want to risk damaging other parts.

Hey again! Yeah, the repair came to 515 € for fixing the faulty injector. Money well spent though, my M3 has been running like a dream since then! The excessive fuel consumption issue cleared up immediately, and the engine's back to its smooth, powerful self. It's such a relief not seeing that check engine light anymore, and the car feels properly balanced now, no more of that annoying jerky acceleration. The mechanic sorted out the rich fuel mixture problem completely, which was causing all those headaches. Honestly, getting it fixed was the best decision. These modern BMWs are amazing machines when everything's working right, but when something's off, it's best to tackle it straight away. Haven't had a single issue since the repair, and it's been several months now. Good call on getting yours checked out quickly, you really don't want to let these things linger. Let us know how it goes!

Just wanted to update you all on what happened with my M4. Finally got it checked out at a reputable shop, and guess what? You were spot on! Had two injectors that needed replacement, plus they found a minor vacuum leak that was contributing to the problem. The whole thing set me back about 800 bucks, but honestly, it was worth every penny. Picked up the car yesterday and it's running like new again, smooth power delivery, normal fuel consumption, and that annoying check engine light is finally gone! The acceleration is back to being crisp and responsive, just like it should be. Really glad I didn't wait any longer to get it fixed. The mechanic was super professional and walked me through everything they did. They even showed me the old injectors, you could clearly see they were gunked up. Thanks again for pushing me to get it sorted quickly. You definitely saved me from potentially bigger problems down the road.

Good day I really don't know what to do anymore. I have checked the lambda sensor, the mass air flow sensor, the injectors and the intake bridge for leaks but it is still giving me the error mixture control I don't know where to look anymore. I drive a bmw e93 with n53 325i I would be happy if you could help me.

(Translated from German)

Check the condition of your spark plugs and ignition coils. Worn or faulty spark plugs and coils can cause mixture control issues by affecting combustion efficiency. If they haven't been replaced recently, consider inspecting and replacing them as needed. Let me know how it goes or if you have any further questions!