Still multiple misfire

Checked the fuel pressure on my 1996 4.0 and it is 50psi no matter what you do to the throttle.

I just put a rear 02 sensor in that had been missing for a while. I changed into a different distributor since the one I had was pertty sloppy and was eating the crap out of rotors and caps. New plugs and new wires. She runs better after the computer gets cleared and over a few days worth of driving she gets progressively worse. Finally on about day three she bucks and shudders at about 50 mph. Only other thing I can figure is a CPS going bad or something? #2 cylinder seems to be running richer than other cylinders. I'm gonna do a compression check this weekend. IDEAS ? ? ? ? ?

is the distributor installed correctly?

Yes it is. It was originally a tooth off when we first installed it but we adjusted it back a tooth and now it works fine. In my experience the jeep will run but it will run pretty crappy if you are plus or minus a tooth, but anything beyond that it won't hardly run at all.

I just changed the CPS on my 2.5L, it was like night and day how much the driveability improved with a new CPS.

But I was NOT getting any misfire codes on my '95 XJ, NOT sure if the '95 Chrysler system checks for them and stores a code, I know later Chrysler systems do, because I own a '99 and '02 Dodge and they will set misfire codes. My motor often felt like it was missing, even if there were no codes for it, using higher octane fuel improved it some, but it looks like a new CPS cured it totally.

Are you getting misfire codes? OR Are you judging misfires by the feel and reaction of the engine?

The Haynes manual has a test with an ohm meter to tell if the CPS is bad, unfortunately, the manual screwed up the instructions, saying "check the resistance over tabs B and C, if there is NO resistance (open) the CPS is good." Do some googling, maybe you find the proper directions to do the test.

yeah I've got a decent code reader and even after clearing the codes I get "random multiple misfire" code and "misfire cylinder # 1,2,3,4,5,6" so I get like seven codes within a minute or so of starting the thing up. I thought about checking the CPS but I have heard that even some that test good are actually bad.

I got my CPS from RockAuto.com, they are NOT cheap, $50 - $70. Plenty of people have seen immediate improvement from a new CPS, but it might NOT be your problem and you just threw money away.

You could look at it, as just improving the reliability of the motor.

Replacing it on my 2.5L was easy, cleaning out the dirt and gunk took the most time. It may be a lot harder on the more crowded 4.0L.

I've removed them on 4.0's before. The only thing that I hate about doing it is the opportunity to drop the screws down in the bellhousing. I'll probably just pull the trigger and do it since it is good to have a trail spare sensor in case somone elses craps out. I'm running out of things to replace at this point.

Just found some info on carbon deposits on the exhaust valves causing the valves to not close completely and therefore causing multiple misfires. Not too sure how common this is but I think I see a can of seafoam and alot of smoke in my future.