Black Smoke & Poor Performance: M Diesel Mystery Help

Hey there, I had similar symptoms with my 2013 Infiniti QX70 Diesel last year at around 65K km. Turned out to be a defective fuel injector. The symptoms you're describing especially the black smoke, weak performance, and jerking match exactly what I experienced. Had it checked at the dealership (after my regular mechanic couldn't properly diagnose it), and their diagnostic test confirmed a faulty injector. They had to replace one injector and clean the others. It was definitely a serious issue that needed immediate attention because it could've damaged other engine components if left unfixed. After the repair, the difference was like night and day smooth acceleration, normal fuel consumption, and no more black smoke. These symptoms aren't something to ignore, especially in a diesel engine. If you're in doubt about mechanics, I'd honestly recommend going straight to an Infiniti dealership for this one. Injector issues need proper diagnostic equipment and expertise, particularly with these engines. Best of luck!

Thanks a lot for sharing your experience! That's super helpful. It does sound really similar to what I'm dealing with. Just curious do you remember roughly how much you ended up paying for the injector replacement and cleaning? Also, has everything been running smoothly since then, or have you had any other issues pop up?

Hey again! Happy to help with an update! Yes, just got the car back last week after taking your advice and going to the Infiniti dealership. You were spot on it was indeed a faulty injector causing the lean mixture issue. The total bill came to 515€ (including parts, labor, and cleaning the other injectors). Since the repair, my QX70 has been running like new again! The error code for the lean mixture is completely gone, and all those annoying symptoms disappeared. No more black smoke, jerking, or poor fuel economy. The engine feels strong and smooth again, just like it should. Haven't had any other issues pop up since then it's been smooth sailing. Really glad I didn't wait any longer to get it fixed, as the mechanic mentioned it could've gotten much worse (and more expensive!) if left unchecked. If you're still dealing with similar symptoms, I'd definitely recommend getting it checked out at the dealership. The peace of mind is worth it, even if it costs a bit more than a regular mechanic. Let me know if you need any other info!

Thanks so much for the detailed follow-up! That's actually not as expensive as I feared. I bit the bullet and took your advice went to the Infiniti dealership yesterday. What a difference from my last mechanic experience! They diagnosed it right away, and you're right again bad injector. Getting it fixed tomorrow. Funny thing is, I was so worried about getting ripped off that I almost kept putting it off. The quote they gave me is pretty close to what you paid, which makes me feel a lot better about the whole thing. Really appreciate you sharing your experience it gave me the push I needed to get this sorted. I'll definitely update my car's maintenance schedule moving forward to catch these issues early. Lesson learned about not waiting too long when these symptoms show up! Thanks again for all your help you saved me from a lot more headaches (and probably a bigger repair bill down the road)!