BMW 5 Series Power Loss & Smoke: Possible Knock Issue?

Hey there! I've got some experience with BMWs (low experience) and faced something very similar with my 2013 BMW 3 series. Had those exact symptoms, reduced power, jerking, and that annoying emergency mode popping up. Took it to my regular workshop and turned out it was carbon deposits buildup in the combustion chamber. The fix wasn't cheap, set me back about 425 Euro for a thorough cleaning and service. But it sorted out all those issues and the car's been running smooth since then. Could definitely be the same problem you're having, but mind sharing which engine variant you've got in your 5 series? Also, what's your mileage? That'd help me give you more specific info about what I learned from my experience.

Thanks for sharing that! My 5 series has 124903 KM on the clock and just to add, I had similar symptoms when my spark plugs were on their way out. Got them replaced during my last service and it helped for a while, but now the issues are back. Could be connected to those carbon deposits you mentioned. Did your mechanic mention how often this cleaning should be done as preventive maintenance?

Hey again! Yeah, I totally get what you're saying about the spark plugs, that was actually my first thought with my 3 series too. When I had the carbon deposit issue, my mechanic told me that cleaning should ideally be done every 60,000 to 80,000 KM, especially for direct injection engines like ours. But honestly, it really depends on your driving style and the fuel quality you're using. After my experience, I started using better quality fuel and fuel system cleaners every 15,000 KM or so. Been doing this for about a year now, and it seems to help prevent the buildup from getting bad again. My mechanic also mentioned that shorter trips where the engine doesn't get fully warm can make the carbon build up faster. Since you mentioned your spark plugs helped temporarily, it might be worth checking both issues, could be carbon deposits making your new plugs work harder than they should. In my case, I also noticed the car ran much smoother after the cleaning, and fuel consumption improved a bit too. Have you noticed any changes in your fuel consumption lately? That was another telltale sign in my situation before I got it fixed.

Thanks for all that detailed info! Yeah, now that you mention it, I've definitely noticed my fuel consumption going up lately, probably using about 2-3 liters more per 100 KM than usual. That's really helpful to know about the cleaning schedule and using better fuel. Makes total sense about those short trips too, I do a lot of those for work. Think I'll book it in for a proper check and cleaning. At my mileage, it's probably well overdue for that carbon deposit removal you mentioned. Will also look into those fuel system cleaners you're using, sounds like a smart preventive measure. Rather spend a bit on maintenance now than deal with bigger issues later. Really appreciate you taking the time to share your experience. It's given me a much clearer picture of what I'm dealing with. Better get on this before it gets worse!