BMW M4 Power Loss and Smoke: EGR Valve Crisis?

Had the exact same symptoms on my 2018 BMW M2. The rough idle, power loss, and excessive smoke were spot on identical to what you're describing. The EGR valve was indeed the culprit, it was stuck open and causing all sorts of chaos. Had it fixed at a garage last month. The mechanic found that carbon buildup had jammed the valve, preventing it from closing properly. This was letting exhaust gases flow back into the intake when they shouldn't. They had to remove the valve, clean everything thoroughly, and ended up replacing the whole unit since it was pretty damaged. It's definitely a serious issue that needs immediate attention, running the car like this can lead to bigger problems with the engine. The repair itself wasn't super complex, but leaving it unfixed could damage other components. My advice would be to get it checked ASAP. The symptoms you're describing match my experience perfectly, and it's not something you want to ignore.

you're describing exactly what happened to my M4 back then! Totally get what you went through with that EGR valve nightmare. Quick question though, do you remember roughly how much you had to shell out for the repair? And has everything been running smoothly since you got it fixed, or have you noticed any other issues popping up? Just want to make sure I'm prepared for what might be coming my way with this repair.

Hey again! Yeah, I got it all sorted, spent exactly 355€ to fix that troublesome EGR valve, and I've got to say it was worth every penny. Since getting it fixed up, my M2's been running like an absolute dream, no more of that annoying power loss or those pesky smoke issues we talked about earlier. The mechanic did a proper job cleaning out all that carbon buildup and replacing the jammed valve. It's like having a completely different car now, smooth idle, proper power delivery, and no more check engine lights giving me grief. Fuel consumption's back to normal too, which is a nice bonus for the wallet. Haven't had a single problem since the repair, and it's been about six weeks now. Trust me, once you get yours sorted, you'll notice the difference straight away. Just make sure they do a thorough clean of the whole system while they're at it, that's what really made the difference in my case. Let me know how you get on with yours!

Thanks for all that info! Just got back from the mechanic today actually. You wouldn't believe it, my repair bill came in higher at 520€ because they found some additional gunk that needed cleaning out. But hey, money well spent if you ask me! The whole experience was way better than my last mechanic horror story. This guy really knew his BMWs and walked me through everything he was doing. Took about four hours total, but the difference is incredible. The engine's purring again, no more smoke shows when I accelerate, and that annoying power loss is completely gone. Funny thing is, while I was there, another guy came in with the exact same issue on his M3. Seems like these EGR valves are quite the troublemakers in our beemers! Anyway, really appreciate you sharing your experience, it gave me the confidence to get it sorted before it turned into something worse. Car's running like new now, and I couldn't be happier with the result.