QX Diesel Issues: Black Smoke & Cold Start Problems

Hey there! I have some experience with diesel engines. Had a similar issue with my 2011 Infiniti FX Diesel. Similar symptoms black smoke, hard starts, and that annoying pre-glow light staying on. Turned out the wiring harness connecting the glow control unit to the digital diesel electronics was damaged. My trusted mechanic spotted it during inspection cost me around 155€ to fix it completely. After that, all those issues disappeared. Before I share more specific details about my experience, have you scanned for error codes? Any unusual sounds when starting? How many miles/km on your QX? These details would help me better compare our situations and maybe point you in the right direction!

Thanks for the reply! Yeah, I'm sitting at 99013 KM and just had my service done recently. Haven't noticed any weird sounds during start-up, but I haven't scanned for codes yet planning to do that tomorrow. Your wiring harness situation sounds pretty similar to what I'm experiencing. Definitely worth checking out, especially since your fix wasn't too expensive. I'll get those codes and update you guys soon.

Hey again! That's good you're getting those codes checked that'll help a lot. Just thinking back to my FX's issues, mine started showing these problems around 95,000 KM, pretty close to where you're at now. When my mechanic found that damaged wiring harness, he actually showed it to me there was some obvious wear where the wires had been rubbing against a bracket. Apparently, it's a fairly common issue with our models once they hit higher mileage. The black smoke in my case was because the glow plugs weren't getting the right signals due to that damaged wiring. Just a heads up while you're getting it checked, might be worth having them look at the glow plug connections too. In my case, they found one plug was a bit corroded. Didn't cost much extra to clean it up while they were in there. Keep us posted about those codes! If they're anything like what I got (I remember getting P0380 and P0671), it'll probably point to the same issue. The best part was how quickly everything cleared up after the fix no more black smoke, started like new, and that annoying pre-glow light finally behaved itself!

Thanks so much for all the detailed info! This is really helpful, especially knowing about the common wear point on the wiring harness. I'll definitely ask my mechanic to check both the harness and those glow plug connections. It's actually reassuring to hear that yours started acting up around the same mileage makes me feel like I'm not just unlucky! Just got back from scanning the codes, and guess what? Got P0380 among others, just like you did. Looks like you were spot on! I've already scheduled an appointment with my mechanic for next week and shared your experience with him. Really appreciate you taking the time to share all this helped me feel much more confident about what might be wrong. I'll update this thread once it's fixed in case anyone else runs into the same problem.