96 XJ stumbles while idling and misfires while driving

Hey Everyone so i have been dealing with this issue for probably about 2 or 3 months, just haven't had time with work to sit down for a day and diag it 100%, so im going to go through what i did do after i say what is happening. Yes i had searched the forums but it seems that i have replaced everything that everyone had solved there issue with

So the XJ would run great and one day my buddy was driving the truck said the truck was missing it seemed like which wasn't a big deal he brought it over had a code for an O2 sensor, so I changed both of them and it didn't do it again for some time. I figured it was nice out one day ill take the doors off and drive the jeep ran great for about 2 hours. while i was driving it miss/hiccup at any speed or RPM, then about 5 minutes later it died with a crank no start. towed it back to my house and the CPS wasn't reading so i replaced that with a Autozone one ( yes i know i shouldn't have done that ) the truck ran great then a week later while driving around running some errands it missed again. got it back to my house and then it wouldn't start again. Got a mopar CPS this time and brought he other back as a warranty and got a credit. driving the truck now it is still missing/hiccuping but it never stalls just rough running whether at idle or driving. Changed plugs wires cap and rotor since they hadnt been done in a while. That didnt work, i put a new distributor in since i thought maybe it was the sensor in the distributor shutting the truck off, nope still having the same issue. Then i read TPS could have problems figured well ill change that since it was a few buck and still doing the same problem. I am lost with this truck. I had a scan told on it viewing live parameters and did not see anything out of the ordinary.

So over the past i would say 8-9 months i had done
- Both O2 sensors
- Mopar Crank sensor
- Plugs (autolite) never had a problem with them before
- Wires (duralast)
- New distributor (duralast)
- New TPS (duralast)

Truck has 190k on it and has always been go and i never had problems, the truck had a new Bosch fuel pump put in about 2.5 - 3 years ago and i checked fuel pressure it is about 40 KOEO and while running around 35, i am going to change the fuel filter Tuesday after work but just want to get some ideas on what to check.
:dunno::dunno:

The truck still runs and drives, and it does not die out neither, just very rough running with a miss or hiccup here and there and then will driving the truck light throttle or heavy it missfires and backfires non stop

If the 96 has an FPR at the front of the fuel rail, the vacuum line to should be checked for signs of leaking gas from the FPR diaphragm. Also check the vacuum hose from the throttle body to the MAP sensor, mounted on the throttle body, I think, in 96? If not it is on the firewall. Check for >12 volts at the O2 sensor heater wires at the sensors and check the ground wires in the harness for the O2 sensors. If no 12 volts, check the fuse or relay for the O2 sensor heater (not sure which the 96 has).

Also check the HV coil and the ICM (Google this forum for old threads on testing them, wire color, volts....)

Lastly do a leak down test on the fuel rail pressure with the engine off (prime it first) to see if the FPR or fuel injectors are leaking.

That's all Ive got. Look for damaged wires near the exhaust system and drive shafts.

'96 should not have an FPR on the fuel rail. That should be in the tank. And pressure should be 49 psi. I suspect that is your problem.

This might be of some use to you: http://www.naxja.org/forum/showthread.php?t=1107991

Thanks Ecomike and Anak i will have to check those things, i know the FPR is not on the rail so i guess i will check FP again and drop the tank if not set at 49 like it should be.

Funny thing is it has been at around 40PSI the whole time since ive changed the pump and it always ran fine just out of know where it started to do this funny business.

There's no need to drop the tank on a 96; you can angle the pump out from
underneath easily. I agree it's probably a fuel delivery issue, but might not
be the pump itself. Boschs are pretty reliable.

Might be a partially clogged fuel filter.

Unless all the in-tank soft hoses were replaced during the fuel pump work,
there might be a split in one of them that allows pressure to be reduced
to the fuel rail. This would explain the erratic/low pressure readings.

I've seen this many times. The split will be almost invisible so you really
have to look for it. It might be near one of the hose clamps.

Thanks for all of the input everyone I am going to try some of tests and confirm the readings I had and will test the suggestions I really hope I figure it out soon and will keep everyone updated

Just an oddball suggestion here. I was having similar issue recently. Turned out to be a loose connector to the Throttle Position Sensor on the throttle body. The snap clip did just that a while ago. It snapped off and the connector backs out a bit from time to time.


Also mine is a 96 4.0