Xj problem

I have a problem with my 90 model and I am looking for ideas. The jeep starts fine but has a dead spot around 1000 to 1350rpm. It will rev past the dead spot but as soon as it idles down it will die. It will refire just fine and idle after that. It has also started to idle rough after about 5 minutes of run time. I have checked the common renix grounds. It has a new fuel pump, filter, pressure regulator, O2 sensor, and recent plugs and wires. I have checked the fuel pressure and it reads fine. On a diagnostic scan the only thing that checked bad was the O2 sensor which I replaced and it still didnt fix the problem. Any ideas are greatly appreciated. I have been looking around at the site for a long time, just never registered until now.

Not always done, but highly recommended--please give as much tech info as possible--year/engine/transmission, and anything else you feel is pertinent.

Ok, that said, your 90 Renix has a dead spot in the throttle and then dies when it tries to return to idle. Have you tested the TPS with an analog multimeter to determine if it has a bad spot? Have you checked the TPS values and adjusted it?

Sorry. Its a 90 model 4.0, auto. I have tested the tps with a meter and it checked out okay.

The harness for the O2 sensor, engine temp. sensor and knock sensor, runs up the front of the block. Often if the intake has ever been removed the harness gets inadvertently rerouted and can cook on the exhaust manifold. You'll need a small mirror and a flashlight, worth a look even if this isn't your problem.
Does anything change after the motor has warmed up? The IAC is always suspect for a cleaning and a little lubrication. This can cause the stalling, though I doubt it has anything to do with the 1000-1350 RPM dead spot. Again worth a look, even if this isn't your main problem.
Do an ohm test and clean the connector for the CPS. Check your MAP vacuum line for a rub through or cracks. Again just something to check for elimination purposes.
TPS sounds like a likely suspect, like mentioned. I had one with a dead spot at around 1/3 throttle.

The problem seems to get worse when the jeep warms up. I have check for vacume leaks and fixed the only one that I found. The hose to the MAP sensor is good. I will look at the harness for wear marks. I just picked up a new CPS today. I am going to install it tomorrow. Thanks for the ideas.

Swapping sensors doesn't necessarily eliminate that sensor as a problem. In my experience better than half the time, the problem is in the connectors or the harness.
Being a cheap skate, on a budget, I usually check the wiring before I buy a sensor. Unless the sensor problem is obvious.
I keep a good set of junk yard sensors, just for comparison tests. I actually replace very few, no more than half a dozen on two Renix's in twenty some years.
Like mentioned in other posts, the motor has to breath right, air cleaner, Cat and compression is likely to show problems at low and high RPM's and may run fine in the mid range. Though overall performance will likely suffer, but be less noticeable once the motor is running near peak torque.

When you tested the TPS with the analog meter did the voltage change smoothly throughout the throttle's full range?

Yes it did.

I know you said it's new but, it sure sounds like the O2 sensor to me. Exact same issues I had and that is what it was.

Wire to 02 sensor cooked?

The wire looked good. I will gwt the scanner back on it later this week and see if the new O2 reads bad. I just picked up a complete harness, ecm, intake, throttle body, manifold, and a few other parts form a friend for $50. I'm going to try the tps off of that throttle body and see if it changes anything. I will try the other O2 sensor too.

Just replaced the CPS and the TPS and its still not fixed. Any more ideas?

Clogged catalytic convertor can be checked with a vacuum gage. Hook up to intake. If vacuum steadily decrease, it's an indication of a clogged exhaust.