3500 rpms max

[heavyequipment]

I'm working on my '90 Cherokee 4.0L, 4wd, auto. Mostly, it runs very well, but sometimes when I floorboard the accelerator and keep it down, it craps out around 3500 rpm, not fast enough to shift out of first. Sometimes it runs normally. It has new plugs, wires, cap, and rotor, and new fuel and air filters. I changed the fuel filter after the first time this happened. The other stuff was new before. I installed a new Borla header and a straight-through (cherry bomb) muffler. At that time, I checked the cat and could see through it, through a honeycomb matrix. It seemed to be quite clear. I'm thinking maybe fuel pump, but???

Any ideas? I'm pulling a travel trailer to Idaho in July, and it needs to be 100%.

[piaa_nissan]

It sound like your in the right neighborhood thinking it's the fuel pump, it could be failing under load and causing your problem. Your cat wouldn't have any effect such as you describe. The most common sign they are going bad is when they rattle or look melted or plugged inside. I would have the fuel pressure checked. IIRC there is also a tank filter which could be plugged but they are integrated with the pump assembly. Have you also checked to make sure you have no water in your gas? Does it backfire or sputter? Water could cause issues also.

[heavyequipment]

The intermittent problems are always the hardest...

The fuel strainer in the tank is new. I changed it when I had to replace the short hose inside the tank.

I cut the old fuel filter apart when I replaced it, and saw no sigh of water or rust.

No backfiring or poor running at all. Even when it won't exceed 3500 rpm it's still running smooth...

I might put a fuel pressure gauge on it and drive it around some. Or, I might just change the fuel pump and see what happens.

I hate changing parts to test. I call it the Christmas Tree method of troubleshooting, after how we used to change bulbs in a series-wired string of Christmas lights until we found the bad one.

I was hoping someone had seen this problem before and would reply.

[woodbutcher44]

has the check engine light came on?
is it injected?
sounds like the tps is starting the go bad.
my 95 zj was doing simmaler then started stalling at low speeds . When I replaced the tps it was 4.slow no mow
get a scan or flash it yourself