Black Smoke & Cold Start Issues: QX Diesel Help

Hey there, I had nearly identical issues with my 2017 Infiniti Q50d last winter. The symptoms matched exactly what you're describing black smoke, rough starts in cold weather, and unusual stalling. The check engine light was my first warning too. Turned out the fuel filter heater wiring harness was damaged, causing the whole fuel heating system to malfunction. Had it fixed at the dealership because it needed specific diagnostic tools to properly identify and repair the connection issues. While it wasn't the most complex repair, it was definitely serious enough to require immediate attention since it affects the entire fuel delivery system. In my case, they had to replace the complete wiring harness assembly and connector. The repair took about half a day, and it solved all those issues completely. Haven't had any problems since then. If you're experiencing these symptoms, I wouldn't wait too long to get it checked. Fuel system issues can potentially lead to more expensive repairs if left unaddressed. Consider going to an Infiniti dealership or a specialist who's familiar with diesel systems.

Thanks for sharing your experience that's really helpful! Sounds exactly like what I'm dealing with. Quick question do you remember roughly how much the harness replacement set you back? Also, has everything been running smoothly since the repair, or have you noticed any other quirks pop up? I'm trying to figure out if I should budget for any follow-up work.

Hey again! Yeah, I totally get why you're asking about the costs it's always good to know what you're getting into. For me, the whole thing came to 110 Euro for fixing the fuel filter heater wiring harness and connector. Pretty reasonable considering the headache it was causing! And I've got great news since getting it fixed, my Q50d has been running like a dream! No more black smoke, no more stalling, and it starts up perfectly even on those freezing winter mornings. It's been several months now, and I haven't had a single issue pop up. The repair totally sorted out all those annoying problems I mentioned before. You shouldn't need to worry about any follow-up work once they fix that wiring harness, you should be good to go. The mechanic really nailed it with the diagnosis and repair in my case. Just make sure you get someone who knows what they're doing with Infiniti diesels, and you'll be back on track in no time! Hope this helps give you a better idea of what to expect! Let me know if you need anything else.

Thanks so much for all the detailed info! I actually just got back from the mechanic today. You were spot on it was the fuel filter heater wiring harness. Found a specialist through a who really knew his stuff with Infinitis. The repair cost me a bit more, around 150 Euro, but honestly, it was worth every penny. The guy showed me the damaged wiring and explained everything clearly. Took about 4 hours total, but my car's running like new now! No more black smoke, starts up perfectly, and that annoying check engine light is finally off. Really appreciate you sharing your experience it gave me the confidence to get it sorted instead of putting it off. Feels great to have this fixed before winter really kicks in. Thanks again for helping me out! Cheers!