When my XJ warms up it misses hard under load.
Warmer gets worse. Fuel pressure is 45 psi and upstream O2 is new and downstream is disconnected.
Thanks

What year...when you disconnect 1 sensor, both are ignored. Try disconnecting the temp sensor in tstat..fuel regulation is based on temp..higher temp is leaner untill its an open circut then it goes to pre program schedule

Have you checked for codes yet?
Do that first.

Like said, codes. Got any? If so, what are they? Why is the downstream o2 disconnected? And what brand is the upstream o2?

And what year? Almost missed that. It says 2021 XJ under your name but there was no XJ after 2001.

Clean your grounds haha. I always put this now if nobody else says it first. It effects so much and it's free to do.

Not enough info.

4.0 has variable miss. Drive able if I baby it. Pops through intake and exhaust. New cap n rotor, CPS, speed sensor. Fuel is 40 lbs.

Check the timing.

Did you cross a plug wire when you put the new cap and rotor on?

Was this before or after replacing those parts? What brand parts? If you used Haynes to wire the cap, the firing order is off. And how old are those plug wires? You replaced the cap and rotor, but no mention of the plug wires.

Doublecheck the cap to be sure.

Dupe thread...

EDIT: Since the mod merged the threads, no need for the link.

My '99 Cherokee 4.0 4X4 automatic has a severe miss. New CPS, speed sensor, cap n rotor, plugs. Pops through intake and exhaust.

First things first, did you double check to make sure that your plug wires are in the correct order? did it start before or after replacing the parts?

You've made three separate posts on this topic but haven't bothered to respond to anyone trying to help you out. There are a lot of friendly people here who will gladly try to help you solve your problems. But you need to provide more information and communicate in the threads you start if you hope to get help.

I suggest starting here: https://www.cherokeeforum.com/f2/miss-261317/

Good luck!