Black Smoke & Power Loss: Q Diesel's Turbo Warning Signs

Hey there! I had similar issues with my 2014 Infiniti QX70d last year. Based on what you're describing, it sounds exactly like the waste gate valve problem I experienced. The symptoms match perfectly the black smoke, power loss, and that distinctive hissing sound. In my case, the waste gate valve was stuck partially open, which messed up the turbo boost pressure. Had it checked at the dealer's workshop, and they confirmed the waste gate actuator was failing. It took them about a day to replace the whole assembly. This isn't something you want to ignore it can lead to bigger turbo problems if left unchecked. The diesel engines in these Infinitis are pretty solid, but the waste gate components do wear out eventually. Got mine fixed at the official Infiniti service center. They know these engines inside out, and I'd really suggest going to them for this kind of issue rather than a general mechanic. Best of luck sorting it out!

Hey, thanks for sharing your experience! That really helped. Quick question do you remember roughly how much you ended up paying for the waste gate valve replacement? Also, has everything been running smoothly since the fix, or have you noticed any other issues pop up? Would be great to know what to expect cost-wise and if it's likely to be a one-and-done fix. Thanks!

Hey again! Yeah, happy to help! So after seeing the mechanic, they actually found it was both the boost pressure sensor and the waste gate valve that needed fixing. I ended up paying 860€ for the waste gate valve replacement not cheap, I know, but it was worth every penny! The good news is that since getting it sorted, my QX70d has been running like a dream! No more black smoke, the power's back to normal, and that annoying hissing sound is completely gone. Been about a year now and I haven't had any related issues pop up. Just getting the boost pressure sensor sorted made a big difference too it was throwing off all the engine management readings before. The car feels much more responsive now, and the fuel economy's actually improved a bit. Trust me, once you get these things fixed, you should be good to go. These Infinitis are pretty solid cars overall just need proper maintenance when these issues come up. Let me know how you get on with yours!

Thanks so much for all the details! I actually just got back from the mechanic today. You were spot on about the waste gate valve! Mine ended up costing about 900€ because they found some additional wear on the connecting parts. The whole experience wasn't as bad as I feared. Found a really good specialist who actually took the time to show me what was wrong. They got it done in about 6 hours, and wow, what a difference! Took it for a test drive, and it's like having a completely different car no more black smoke, the engine's super smooth, and that annoying hissing is history. Funny enough, they also mentioned the boost pressure sensor wasn't actually the problem like I initially thought. Goes to show how similar symptoms can point to different issues. Really glad I asked here first saved me from jumping to conclusions! Thanks again for your help. It's such a relief to have this sorted. Time to enjoy my smoke-free, properly running Infiniti again!