Hey all so ive had this problem for a few months.

I have a 1992 Cherokee xj 4.0 4x4 Auto

I have no power after 3000 rpm. When I accelerate past 3k rpm i stop speeding up. If i floor it it will Jump to 4k rpm but not go past 4k, I also lose all moving power depending on speed the jeep will either start slowing down or maintain the same speed. If I gas it in neutral it will go all the way to rev limiter no issues. So it appears to only do this while under load. Also running a/c or going up a grade the issue will happen at lower rpms ex 2600-3000 rpm

I have checked back pressure 0-1 psi, Fuel Pressure 31 psi and with regulator disconnected 47 psi.

Any help would be much appreciated.

 

fuel press is 31 at 3000 rpm?

 

yes it will fluctuate some but for the most part be right at 30 psi all the way to rev limiter.

 

A common problem seems to be the catalytic converter restricting the motor. Under load the motor makes more exhaust gasses then just in neutral.

 

That's what I originally thought might be happening. So, I did an exhaust back pressure test and it read 0-1 psi from idle to rev limit. The test was conducted when the engine was cool and during normal operating temp.

 

Did you do this while driving? or in the driveway?

 

In the driveway. My gauge is not long enough to reach any farther than driver side tire, and the instructions said not to do while driving.

 

Vacuum test & pay attention to the scenarios listed here....

http://www.secondchancegarage.com/public/186.cfm

 

The problem with this test is that the motor isn't under any load, it is just turning itself.

This is excellent. OP you should definately do a vacum text.

 

That sounds amazing im going to have to pick up a vacuum test kit.

Also, today it started doing it at 1.8k - 2k rpm.

 

Update, so something very peculiar just happened. I started doing a fuel volume test, and my fuel rail has A LOT of air bubbles in it (like half air half fuel)..

 

Solved!!!!!!!!

After seeing all the air in the fuel rail. I pulled the fuel pump and the fuel pump strainer was not there. From my understanding the strainer is important for keeping the fuel pump primed. So I decided being that the pump probably sucked up whatever crap was in the bottom of my gas tank I would just replace the whole unit now while i have the money.

I did buy a vacuum gauge tester. I won't be needing it now but it will be nice to have in the future.

A big thankyou to everyone for their advice and help.