BMW 6 Series EGR Drama: Smoking Engine Mystery Unfolds

Hey there. I had very similar symptoms with my 2012 BMW 5 Series last year. My car was at 145k km when these issues started. Same problems, power loss, black smoke, rough idle, and that distinctive hissing. Was pretty certain it was the EGR valve, and turned out I was right. Mine was completely clogged with carbon deposits and got stuck in the open position. Had to get the whole EGR system cleaned and the valve replaced because it was damaged beyond repair. It was a serious job because the carbon buildup had started affecting the intake manifold too. The mechanic showed me the old valve, it was completely black inside. The repair made a massive difference though. Engine ran smooth again, fuel consumption went back to normal, and all those warning lights disappeared. Not something you want to ignore, if left too long, it can cause bigger engine problems. Would definitely recommend getting it checked out soon. The symptoms you're describing match my experience exactly.

Thanks so much for sharing your experience! Really helpful to hear from someone who went through the same thing. That's actually quite reassuring that your symptoms matched mine so closely and it turned out to be the EGR valve. Do you remember roughly how much you ended up paying for the whole repair? Also, has everything been running smoothly since then, or have you noticed any other issues popping up? Been a bit nervous about potential follow-up problems.

Hey again! Yep, just got back from the mechanic last week actually. You'll be glad to know I was spot on about the EGR valve, it was completely jammed up, just like I suspected. Cost me 355 € to get it sorted, which honestly wasn't as bad as I was expecting given all the hassle it was causing. The car's running like a dream now, all those annoying symptoms we talked about have completely disappeared. No more black smoke, rough idle, or that irritating hissing noise. The engine's got its power back and my fuel consumption's back to normal too. Haven't had a single issue since the repair, and the mechanic did a really thorough job cleaning out all the carbon deposits while they were at it. Trust me, once you get it fixed, you'll notice the difference straight away. The engine just feels so much smoother and more responsive. Honestly, these BMW engines are pretty solid once you sort out these kinds of issues. Just make sure you get it looked at sooner rather than later, leaving it too long can lead to bigger problems down the line.

Thanks for the follow-up! Just got back from the mechanic myself and you were absolutely right. What a relief! Had the EGR valve replaced and the whole system cleaned out. The mechanic showed me the old valve, it was completely gunked up with carbon deposits, exactly like you described. The repair cost me a bit more than yours, around 400 €, but it was worth every penny. The difference is like night and day. No more scary engine light, the hissing's gone, and the engine's running super smooth again. Fuel consumption has dropped back to normal too. Really glad I didn't put this off any longer. The mechanic was actually pretty decent, explained everything clearly and even showed me the old parts. Definitely feeling more confident about my car now. Thanks again for helping me figure this out!