Infiniti FX Running Rich: Black Smoke & Power Loss Issues

Hey there! Had almost the exact same issue with my '02 Infiniti G35 last year (I have some experience working on cars, mostly basic maintenance). Those symptoms sound super familiar my car was doing the same thing, and it turned out to be a bad fuel pressure regulator. Had to take it to my trusted mechanic, Mike's Auto Shop, and they diagnosed it pretty quick. The fix set me back about 250 Euro, but it solved all those issues no more black smoke, jerking, or rich running. What's your current mileage on the FX? Also, have you had any other recent work done on the fuel system? This could help me give you more specific advice since these Infinitis can be a bit tricky sometimes. I've also owned a Q45 before, so I'm pretty familiar with the brand.

Thanks for sharing your experience! I'm at 169434 KM and just had my regular service done last month. That's really helpful info about the fuel pressure regulator the symptoms do sound spot on. Honestly, I was worried it might be something more serious (and expensive!). Gonna get it checked out at my local shop this week. Did you notice any other warning signs before you got yours fixed?

Hey again! Good to hear back from you. Yeah, with my G35, I actually did notice a few warning signs before it got really bad. About a week or two before all those symptoms hit full force, I started noticing a slight hesitation when pressing the gas, especially from a cold start. The fuel economy started dropping gradually too I remember checking my fuel app and seeing it get worse week by week. One thing I didn't mention in my first reply my car had slightly fewer miles than yours (around 155000 KM) when this happened. But these Infinitis are pretty solid, so the mileage isn't necessarily a huge concern. The fact that you just had your regular service done is actually good at least you know it's not something basic like dirty filters. Just a heads up when my mechanic replaced the fuel pressure regulator, they also recommended checking the fuel injectors while they were at it. They ended up being fine in my case, but it might be worth having them looked at since they're dealing with the fuel system anyway. Better safe than sorry, right? Let me know how it goes at the shop! Hope it's the same simple fix I had.

Thanks so much for all the detailed info! That's super interesting about the gradual symptoms you noticed now that you mention it, I did notice my fuel economy getting worse over the past few weeks, just didn't connect the dots. Good call on checking the injectors too definitely gonna mention that to my mechanic when I take it in. Really hoping it's just the fuel pressure regulator like in your case. Will update you once I get it checked out! You've been super helpful, really appreciate you taking the time to share your experience with me.