Infiniti FX Diesel: Black Smoke & Power Loss Mystery

Hey there! I had a similar situation with my 2013 Infiniti QX70 diesel (I have some experience working on cars). The symptoms you're describing sound exactly like what I dealt with last summer. In my case, it turned out to be a damaged wiring harness to the boost pressure actuator the wires were literally frayed and causing all those issues you mentioned. Took it to my regular workshop, and they diagnosed it pretty quickly. The fix wasn't too complicated they replaced the wiring harness, and everything went back to normal. Cost me around 155€ total. No more black smoke, rough running, or power loss since then. Could you share more details about your FX? Like the engine size and mileage? That would help me confirm if we're dealing with the same issue. These Infinitis often have similar patterns when things go wrong.

My mileage is at 138186 KM, and I just had it serviced last month. Thanks for sharing your experience! That's really helpful info about the wiring harness definitely sounds similar to what I'm experiencing. I'll get it checked out at my local workshop. Did you notice if the problems got worse over time before you fixed it? Mine seems to be getting progressively worse, especially during cold starts.

Hey again! Yeah, I totally know what you mean about it getting worse over time. My QX70 definitely followed the same pattern it started as just occasional problems, but it really went downhill fast, especially during those cold mornings. When I think back, before I got the wiring harness fixed, it was getting really bad in the last couple of weeks. The black smoke was getting thicker, and the car would shake like crazy during cold starts. Mine was at about 142,000 KM when this happened, so pretty similar to your mileage. One thing I forgot to mention in my first reply I initially tried cleaning the boost pressure sensor thinking it might help (total waste of time, by the way!). The wiring was the real culprit. Just looking at your mileage and symptoms, I'm even more convinced we had the same issue. Quick tip: when you take it to the workshop, ask them to specifically check the wiring near the firewall that's where mine was frayed. Saved them some diagnostic time knowing exactly where to look. Keep us posted on what you find out! Always curious to hear if my experience helps someone else with these Infinitis.

Thanks so much for the detailed follow-up! That's super helpful, especially the tip about checking the wiring near the firewall. I've just booked it in at my local workshop for tomorrow morning don't want to risk making it worse by driving it too much. Really appreciate you taking the time to share your experience, it's definitely made me feel better about the whole situation. I'll let you know what they find, but based on what you've described, I'm pretty confident it's the same issue. The symptoms match perfectly, especially that bit about it getting worse during cold starts. Fingers crossed it's just the wiring harness and nothing more serious! Thanks again for all your help!