BMW X6 Diesel: Preheating Issues and Heavy Smoke

Hey there! I have some experience working on cars and faced something very similar with my 2006 BMW X5 diesel last winter. The symptoms were almost identical to what you're describing. After taking it to my trusted workshop, it turned out to be a faulty wiring connection to the glow plug control module. The cables had corroded over time, causing intermittent connections. The repair itself wasn't too complex, they replaced the damaged wiring and connectors. Cost me about 95 Euro and solved all those issues: the smoking, hard starts, and warning lights disappeared. I actually switched from an X5 to a BMW X3 recently, and keeping the electrical connections clean and protected has been a priority for me since that experience. Before I can give more specific advice, could you share: Current mileage on your X6? Did you scan for specific error codes? How long has this been happening? This would help determine if you're dealing with the same issue I had or if it might be something else.

Thanks for sharing your experience! My X6 has 171273 KM on the clock and I just got her serviced last month. I did get the error codes scanned at a local shop, they showed P0380 and P0670 which point to the glow plug system. The issue started about three weeks ago when temperatures dropped. Your wiring problem definitely sounds similar to what I'm experiencing. The smoking and hard starts are exactly the same symptoms. Good to know it wasn't a massive repair job in your case. I'll definitely have my mechanic check the wiring connections first before replacing any major parts. Was your car also struggling with acceleration when you had this problem? Mine feels a bit sluggish especially when cold.

Hey again! Yes, my X5 definitely had that same sluggish feeling during acceleration when it was cold. I remember it was particularly noticeable in the mornings. Those error codes you mentioned (P0380 and P0670) are exactly what I saw on mine too. The cold weather really exposes these wiring issues, that's when my car would act up the most. With 171k on your clock, it's about the same mileage range where I started having these problems. One thing I didn't mention in my first reply, I also noticed my fuel consumption went up a bit during this period, not sure if you're experiencing that too? The smoking during acceleration was probably the most annoying part for me, especially since I was worried about failing emissions tests. But once the wiring was fixed, the engine ran smooth as butter again. Just a heads up, while my issue was the wiring, make sure your mechanic checks the glow plugs themselves too. Mine were actually okay, but sometimes they can be worn out at this mileage. The symptoms can be pretty much identical, and it's worth checking while they're in there anyway. Let me know how it goes after you get it checked out. I'm curious if it turns out to be the same issue I had with mine.

Thanks for the additional info, and yes, now that you mention it, I have noticed the fuel consumption has gone up! I was actually wondering about that but didn't connect it to these other issues. Been filling up more frequently than usual these past few weeks. Really appreciate you mentioning about checking the glow plugs themselves. I'll definitely ask my mechanic to inspect those while they're looking at the wiring. Makes total sense to check everything while they're working on that system. Would be annoying to fix the wiring only to have to go back in for the plugs later. I've booked it in for next week, so I'll update you once I know what they find. Fingers crossed it's just the wiring like in your case. The fact that we had the same error codes makes me feel pretty optimistic about it. Thanks again for all your help with this, it's really useful going in to the mechanic with some specific things to ask them to check!