King89

I am in the process of researching, but also wanted to post and see if I could glean any insight into my issue. I've been repairing issues on my xj one after another lately. I just finished replacing the Rms, oil pan gasket, and front tranny pump seal. Everything is buttoned up. New fuel injectors installed. On start up I had no oil pressure and a check gauges light. Investigation revealed bad oil pressure sensor. That has been replaced. Had to change a couple hose clamps and radiator cap to stop a leak on the coolant system. But on start up this time I get an issue I'm chasing.

I get a high idle on start up that settles.
Then begins to slow and chug, resumes idle.
Any application of the pedal makes it chug and shudder.
Check gauges kicks on
Battery gauges drops from 14 to 9
No codes thrown on the obd reader

I thought maybe the fuel pump wasn't able to keep up due to bad alternator. So I pulled it for testing and it checked off as good.

What's the most likely cause, and where would you start? Some relay or fuses related to the fuell or charging system, TPS, CPS, fuel pump, injectors that were installed, or something else?

Any help is appreciated.

Also over the last 1.5 year I have replaced the following:

Bosch fuel pump
TPS (Mopar)
CPS (Napa)
Ignition coil
Distributor
Rotor button and cap
Alternator
Sparkplugs
Wires
Cam sensor
Valve cover gasket
Trans seal
Radiator cap
Thermostat
Temp sensor
Oil pressure sensor
Muffler
O2 sensors

​​​​​
​​​​
​​​

King89

Also this is on a 1998 xj sport 4.0l Aw4 4x4

jordan96xj

That's a lot to digest, but the first focus is the voltage. Perform voltage test using meter at the battery with engine running, to see if you can confirm that system voltage is actually dropping as low as 9 volts. Don't just go by the gauge. If you confirm that is happening, then that has to be the first thing to follow.

Have you cleaned and tightened every battery, ground, and alternator connection?

4.3L XJ

The first thing I would do is clean the idle air controller on the throttle body. It sounds sluggish. You are getting the voltage drop I think from the very low engine rpm, and hence the check gauges light. Should be an easy fix. On the gas pedal issue, two things to consider. O2 sensor if the engine has been on awhile and throttle position sensor.

King89

I haven't checked those yet. It was incredibly cold today. I'm going to check all grounds and verify terminals and voltage check tomorrow while the sun is out.