Heres the rundown. 89 xj 4.o auto 4WD "RENIX" pretty much stock. I was driving it down the interstate and it just loses power... no noise no indication of problems just suddenly loses power ( did not cut off)and when you try to make it go it starts to backfire and hesitate....

So I removed the cat.. cleaned and tested the injectors installed all new o rings. installed a new cps, tps, 2 new fuel pumps( the first was weak). Also new fuel pressure regulator. ..the plugs and wires and caps all less than 3 months old.
It was running like a dream... no hesitation no pops smooth and strong.. O Happy day ...Except it was way too loud ( no cat and a bad muffler)so I had a new tail pipe and muffler installed ( still no cat)

then this happens

.... Now it starts ok and runs smooth as silk for about 5 minutes then it starts to hesitate and backfire through the throttle body. but only under load during acceleration. I found out that if I turn the engine off and then restart is is ok again for a couple of minute then it returns to acting up..... it idles fine and revs smoothly in place. ign control module test good....31 psi on fuel rail. 40 with vacum removed. So its not the pump again..

... where do I go from here ............ ? coil... o2 sensor, distributor what is next....

 

Quit throwing parts at it..Do a fuel pressure test.

Have you ever clicked on the pink link in my signature and done any of the ground refreshing and such?

 

I had stated that i got 31psi and 40 when I removed the the vacuum line from the fuel pressure regulator pressure.

I went through the sensor checks following the instructions found here

]http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm[/URL]

I haven't gotten to the temp sending unit that feed the ecu, the temp unit that feeds the gauge seems to work well.

if something did not test out or couldn't be adjusted i replaced it.

It idles smoothly revs easily when parked.

but after i get it on the road and under load. it runs great for about 5 minute or so. then it starts its hesitation and back firing when i try to accelerate form a stop i\light or stop sign .

even after it starts acting up i can pull over, put the jeep in park or neutral and it revs smoothly with no hesitation or popping

it only does it when i am accelerating while driving??

 

You may not have enough fuel pressure/volume at speed/load.

But, have you ever clicked on the pink link in my signature? I would do what's outlined in posts 1,3, 4, and 5.

 

Well I finally got the problem fixed.... all this time it was a bad distributor