Black Smoke & Power Loss: Infiniti M Exhaust Crisis

Had a similar situation with my 2005 Infiniti G35 last summer. One faulty lambda sensor caused pretty much identical symptoms black smoke, drop in power, and that annoying exhaust smell. The check engine light was my first clue. When I took it to the shop, they found that alongside the bad sensor, there was a small crack in the exhaust manifold causing those fumes to leak into the cabin. The sensor issue was making the engine run rich (too much fuel), hence the black smoke. It wasn't a super complex fix, but definitely not something to ignore since it affects emissions and fuel economy. If you're in that situation, I wouldn't put off getting it checked. The sensor itself isn't a major repair, but if you've got an exhaust leak too, that needs attention. My car runs like new now after getting both issues sorted. Found a good independent shop that specializes in Infinitis and Nissans makes a big difference when they know these engines well.

Thanks for sharing your experience! That's really helpful. Mine sounds pretty similar to what you went through. Can you remember roughly how much you ended up paying for the repairs? Also, has everything been running smoothly since then, or have you had any other issues pop up?

Hey again! Just wanted to update you on my G35 repairs it actually cost me 375€ to replace the faulty lambda sensor. After visiting the mechanic, the exhaust aftertreatment malfunction was completely fixed, and I haven't had any problems since. The car's running like a dream now no more black smoke, full power back, and that annoying exhaust smell is totally gone. I'd definitely say it was worth every penny, especially since these issues can get worse (and more expensive!) if you leave them too long. My fuel economy has actually improved quite a bit too, so I'm probably making some of that money back already. Haven't had any other problems pop up since the fix. Just regular maintenance stuff like oil changes, but nothing major. If your symptoms are similar to what I had, I'd say you're probably looking at the same kind of repair. Hope this helps with your decision making!

Thanks so much for all the info! I actually just got back from the mechanic today. You were spot on it was a faulty lambda sensor and a small crack in the exhaust system. Ended up paying about 450€ total, a bit more than yours but they had to patch up that crack too. Got it all sorted now and what a difference! The car's running super smooth, no more black smoke when I accelerate, and that nasty exhaust smell is gone. Such a relief! The mechanic I found was really good too explained everything clearly and didn't try to upsell me on stuff I didn't need. Definitely glad I didn't wait any longer to get it fixed. Feels like I'm driving a different car now. Thanks again for sharing your experience really helped me make the decision to get it checked out right away!