M3 Running Rough: Camshaft Sensor or Something Worse?

Hey there! I had nearly identical issues with my 2012 BMW M5 last year. The symptoms you're describing match exactly what I experienced, rough idle, stalling, and hesitation during acceleration. Initially, I also thought it was just the camshaft sensor. Turned out the encoder wheel on both camshafts was defective, it's a known issue in these engines. The mechanic showed me how the teeth on the encoder wheels were worn down, causing incorrect readings to the engine management system. It was actually a pretty serious problem that needed immediate attention to prevent further engine damage. The fix involved replacing both encoder wheels and sensors. The garage had it for about two days. They also recommended doing a full diagnostic scan because these symptoms can sometimes mask other underlying issues. Since the repair, the car's been running like new, no more rough starts or hesitation. I'd definitely get it checked soon though, as driving with these symptoms can lead to bigger problems. Best of luck with the repair.

Thanks so much for sharing your experience! Really helpful to know about those encoder wheels, definitely wasn't expecting that to be the culprit. Just wondering, do you remember roughly how much you ended up paying for the whole repair? Also, has everything stayed running smoothly since then, or have you noticed any other quirks popping up? Would really appreciate knowing what I might be looking at cost-wise before I head to the shop.

Hey again! Just wanted to follow up, I recently got my M5 back from the mechanic and everything was exactly as suspected. The total bill came to 695 € for fixing the defective encoder wheel on the camshafts. Money well spent if you ask me! The car's running absolutely perfect now, smooth as silk! No more of those annoying start-up issues or jerky acceleration. It's been about three months since the repair, and I haven't noticed a single problem. The engine feels strong and responsive, just like it should. Honestly, getting that encoder wheel sorted out made such a massive difference. I can't believe I put up with those symptoms for as long as I did. The mechanic did a great job explaining everything and showing me the worn parts. They also did a thorough check of everything else while they were at it, which gave me peace of mind. If you're experiencing similar issues, I'd say that price is pretty standard for this kind of repair. Better to get it sorted sooner rather than later, trust me, your M3 will thank you for it! Let me know if you need any other info!

Thanks for the detailed follow-up! Finally got my car back from the mechanic today, and you were spot on about the encoder wheels. My issue was actually a bit more complex, turned out I needed both encoder wheels replaced, plus they found a worn-out timing chain tensioner that needed fixing. The total came to quite a bit more than your repair, around 1,200€ all in. But honestly, the difference in how the car runs now is like night and day! The engine starts right up, idles perfectly, and pulls strong through all the gears. No more of that annoying jerking during acceleration. Found a really good mechanic too, he took the time to walk me through everything and even showed me the old parts. Makes such a difference when you find someone trustworthy who knows what they're doing with these cars. Thanks again for your input, it really helped me understand what I was dealing with before heading to the shop. Just glad to have my M3 running properly again!

Hello, by camshaft sensor you mean the sensor and not the valve? Regards

(Translated from German)

If you're referring to the camshaft position sensor, it's different from the camshaft timing solenoid valve (often called the VANOS solenoid in BMWs). The sensor monitors the position of the camshaft, while the solenoid valve adjusts the timing of the camshaft for optimal engine performance. If you're experiencing issues, it's important to clarify which component is being addressed. If you have further questions or need more clarification, feel free to ask!