Assume you meant "Iac" Idle air control. Any new TPS in an 87-90, (at least), needs to be adjusted....CPS is just easy to rule out.

Fuel pressure can be tough. It might flow OK to keep pressure at low flow, idle, than not deliver the flow at work at a higher flow. See what cruiser thinks, but myself if mine did that and i didn't know the history or my fuel filter, I'd at least back-flush it into a mason gar and take a look at the crud, or just replace it. It's just a bit tough, awkward up there on the frame rail. pit falls in your face. No big deal.

 

??? This post was the same as above. ???

 

I bought the Jeep in 2010, it had been setting for 5yrs so I drained and flushed the tank, new sock on the fuel pump, new filter, cleaned the injectors and put on new o-rings, new O2 sensor, complete tune-up. The TPS is adjusted to where it is showing 4.2 volts with the throttle closed. Just put a new fuel filter on 3 months ago.

 

I don't know what the Renix TPS is supposed to read, Cruiser and DFlintstone do, lol. I'm sure there's an adjustment procedure in the links in their sigs.
I do know that a flat or dead spot in the TPS will cause issues at certain throttle positions, might try watching the output on a meter while you slooooowly open the throttle by hand.

 

We can help. First check the sensor ground resistance. Gotta have less than an ohm from those. (Map, 02, TPS ect). Then you loosen the screws on the TPS and set it to 17% of the input voltage explained in Cruisers post #8. Not as hard as it seems! If you have a meter and a calculator we can help you through if need be. I just "blunted" straightened paperclips on my knife stone to make "back probe" pins. You gotta stick something in along side of the wire while it's plugged in to get the reading and do the adjustment. I've never tried normal meter probes.

 

Check the CPS. Be aware of how the wires are supposed to be routed. You may have a bad TPS, at least on the engine side.

The fuel pressure test is a good idea also. Look at the fuel pump ballast resistor on the driver's side inner fender. Loose connections?

 

X3, (at least).

 

After finally getting so time off I checked the CPS wiring and found three spots that had been smashed and/or melted, the melted area only had three wire strands that were unbroken. I replaced the CPS with a new one from NAPA and after doing Cruiser's upgrade on the CPS I installed it. I drove the XJ for a week and had no problems, I even drove to Eugene. OR and back home which is 346 mile drive and still had 1/8th of a tank of fuel left.
Thanks to all who responded with tips on what to check for, I appreciate the support.

 

Cool news. Did you get the wires properly routed?

 

Glad you found the problem! Good job!

Edit..Guys, it's only easy up till 90. Then it's a whole different movie with the HO, OBD, and the three wire CPS with your PCM. Till then we use an ECU, and can simply put an AC digital meter on the CPS output. The post 90 with a PCM uses a feed from the PCM and a spendy meter to check it.

Both DO have a simple resistance check. (at least the earlier does). Might not tell you it's good, but might tell you if it's bad.

 

I did route the harness the right way thanks to your picture Cruiser.