Engine Performance problem
2000 Nissan Frontier 6 cyl Four Wheel Drive Automatic 157000 miles
Filled up on a tank of gas, and that night as I was driving home, the truck felt like it was sputtering, but it only did it a few times. I added a fuel cleaner thinking it was bad gas, but did not work. Since then it has gotten progressively worse, to the point to where it stalls if you are at a stop light. It runs good first thing in the morning for about 5 minutes and then it starts to stumble. I can't drive it because it struggles to maintain any speed when it starts to hicup going down the road, like its needing fuel. It has no DTC, even when it is sputtering. I replaced the MAF sensor because I thought that's what it was, but did not help. Both Ft O2 sensors fluctuate between.800 & .030. And rear O2 are at a steady.300. Whether you are at idle or driving it does the same thing. I starting to think I have a bad fuel pump, but I do not have a pressure tester to check it.
I have a 2000 Frontier V6-Automatic 156k and seem to have the same issues. I had someone try to look at it, but problem didn't repeat. It does only seem to happen when engine has been warmed for a while. Was wondering what you had come across, as far as answers go.