BMW X3 Power Loss + Smoke: What's Behind These Issues?

Hey there! I've got some experience with BMWs, having owned a 2003 BMW X5 before switching to my current 3 Series. What you're describing sounds very familiar. Had almost identical issues with my X5, drop in power, limp mode, jerking, and that annoying smoke. Turned out to be carbon deposits in the combustion chamber. Took it to my regular workshop, and they had to do a thorough cleaning of the chambers and valves. The whole thing cost me around 425 Euro, but it fixed the problem completely. Before I share more specifics about my experience, could you tell me what fault code you're getting? Also, have you noticed if the smoke has a particular color or if it happens more during cold starts? These details would help me confirm if you're dealing with the same issue I had. Just FYI, I've got some experience with car maintenance, but I'm no expert. Just sharing what worked in my case.

Thanks for sharing your experience! My X3 just hit 59528 KM and had its last service two months ago. The fault code I'm getting is P0303, and the smoke is definitely grayish-white, especially when I start the car in the morning. It gets worse when I try to accelerate. Really appreciate the tip about carbon deposits, that makes a lot of sense given the symptoms. I'll get it checked out by my mechanic soon and will update the thread with what they find. The timing seems about right too since these issues typically show up in older BMW engines.

Hey again! Thanks for providing those extra details. The P0303 code actually confirms my suspicions even more, that's a misfire in cylinder 3, which is exactly what I experienced with my X5 before getting it fixed. When you mentioned the grayish-white smoke, especially during cold starts, it's like déjà vu of my situation. In my case, the carbon deposits were really bad in cylinder 3, which explains the specific misfire code. After the cleaning service I mentioned earlier, they also ended up replacing the spark plugs and ignition coils as a preventive measure since they were pretty worn out anyway. The whole job took about 5 hours, but what a difference it made! The engine ran smooth as butter afterward. I checked my old service records, my X5 had around 62000 KM when this happened, so we're in the same ballpark. Just a heads up: when you take it to your mechanic, ask them to check the fuel injectors too. Mine were partially clogged from the carbon buildup, which contributed to the problem. Keep us posted on what your mechanic finds. These BMW engines are generally solid, but they do need this kind of maintenance every now and then. By the way, are you using premium fuel? That helped prevent the issue from coming back in my case.

Thanks everyone for the helpful responses! Just wanted to update you all, I took my X3 to the mechanic yesterday, and turns out you were spot on about the carbon deposits. They did a complete carbon cleaning service, replaced the spark plugs, and checked the fuel injectors. The total bill came to around 500, but honestly, it was worth every penny. The car's running like new again, no more jerking, smoke, or power loss issues. Interesting point about the premium fuel, I've been using regular, but I'm definitely switching to premium from now on. Really glad I asked here before taking it in, helped me have a more informed conversation with my mechanic. They even mentioned that this is pretty common with these engines at around 60000 KM. Thanks again for sharing your experiences. It's really helpful to hear from other BMW owners who've dealt with similar issues. I'll definitely keep up with more regular maintenance to prevent this from happening again!