Black Smoke & Power Loss: FX's Exhaust System Crisis

I have some experience working on cars and had a similar issue with my 2004 Infiniti G35 last summer. The symptoms you're describing sound exactly like what I dealt with black smoke, drop in power, and that annoying CEL. In my case, one of the lambda sensors was shot, and I got it fixed at my regular workshop, AutoTech. The whole thing, including diagnosis and parts, cost me around 375 Euro. My mechanic explained that faulty lambda sensors really mess with the fuel mixture, hence all those symptoms. What's your exact engine size and mileage? That'd help me share more relevant details from my experience. Have you noticed if the symptoms get worse when the engine's warm? Since Infiniti cars from that era share a lot of components (I also looked at the M35 before getting my G35), I might be able to give you more specific pointers once you share those details.

Hey, thanks for sharing your experience with the G35! Mine's at 248295 KM, and I just had it serviced last month. You might be onto something with the lambda sensor the symptoms do sound similar. And yeah, it actually does get worse when the engine warms up. I'm hoping it's just the sensor like in your case and not something more serious. Did you have any warning signs before your sensor completely failed? Also, did your mechanic mention anything about checking other related components while they were at it?

Hey again! Yeah, with my G35, I definitely noticed some warning signs before the lambda sensor completely gave up. For about two weeks before it got really bad, I had occasional stuttering during acceleration, and the fuel consumption started creeping up. Nothing major at first, but it gradually got worse. When my mechanic at AutoTech was fixing it, he actually found that the catalytic converter was also starting to get clogged due to the bad sensor readings. He cleaned it out while he was in there, which probably saved me from a bigger problem down the road. At your mileage (mine was around 230,000 KM when this happened), it's worth having them check the whole exhaust system. Just a heads up if your symptoms are getting worse with engine temperature like mine did, you might want to avoid heavy acceleration until you get it looked at. I learned this the hard way when I tried to pass someone on the highway and got a face full of black smoke in my rearview mirror! By the way, since both our Infinitis share similar engine architecture (my G35 and your FX), there's a good chance the fix will be similar. Just make sure they use OEM parts I tried an aftermarket sensor first to save money, but it didn't last three months. Ended up going OEM anyway.

Thanks so much for all that detailed info! That's really helpful, especially about avoiding the aftermarket parts definitely going to keep that in mind. I'll take it easy on the acceleration until I can get it to the shop. Actually just called AutoTech since you mentioned them, and they can get me in next Tuesday. I'm hoping they can do the same thorough check they did for yours, especially with the catalytic converter inspection. Really appreciate you taking the time to share your experience it's made me feel a lot better about the whole situation. I'll make sure to update the thread once I get it fixed in case anyone else runs into the same issue with their Infiniti.