I have a 98 XJ with a 4.0 130k on it. I bought it a few months ago, and about once every few days it would have sputtering like symptoms, but would last a few seconds and be fine. Then it started to happen everyday, and slowly got worse. Now it does it just about every time I drive it (only after it has warmed up about 3-5 mins into driving it will start) Sometimes it will only last for a few seconds, sometimes 5+ minutes as I limp it home. Also it is very inconsistent and will at times take throttle and can rev up to 4k no problem, then after letting off it will drop down when my foot is off the throttle to 300-600 RPMs, but only has actually stalled on me once.

This past week when in park sitting in the driveway it can idle for 20+ mins 5-6 times and will idle fine and take throttle fine. Can drive around town for 10 miles without it happening. Then the next time I take it out it will go 2 miles and start, and continue the 2 miles back home.

No CEL have ever been on.
Plugs were done when I bought it, as well as Lucas injector cleaner usually every 1500 miles (twice so far) and wires were recently done. All of which had no effect on it.
I replaced the fuel pump thinking that was the issue. But no changes, took off the TB cleaned thoroughly and the sensors on it, and put a new TB gasket, no help.
Any other ideas??
Possibly injectors?
I have heard crank sensors cause strange issues like this?

 

Tps.....
maybe.....

 

I did pull the TPS off and clean it, but did not replace it..

 

O2 sensor(s) ?

 

Haven't really though about 02 sensors, I've had to replace them on my last XJ and my KJ, but they threw a CEL and didn't really effect the running condition. I will pull them out and check them, but I thought they usually threw a code.

 

I've been told many times that a problem with O sensors will trigger an error code. But every time I personally have had to replace one there's been no code and no CEL either. Symptoms have been no power/acceleration. Also a failing catalytic converter displayed same symptoms. I found out the hard way, bad fuel can toast O2 sens' and Cat' without a CEL or codes.

 

In (my) order or likeliness:
Upstream o2 sensor
IAC
TPS
Then in no particular order cause I doubt it:
Vac leak
Bad cat
ECM
CPS
Heater circuit (does horn work and no airbag light on?)

Have you put it on a code reader? I know you said no CEL, but, codes can store in there without tripping CEL.. So IMHO it's always worth a check.. Btw, on the code reader note: a good mechanic with a good diagnostics tool should be able to find something obvious like improper o2 sensor voltage, for example.
One last thought: hesitation, popping at manifold, struggling idle: these are all symptoms of fuel delivery issue...

 

Thanks for the input, I have not actually got checked for codes, but we do have emissions tests, that you can not pass with any stored or recent CELs, which is passed when I first got it.

I will take it up to autozone and get it checked.
I will also look into 02 sensors, as well as the TPS and IAC.