Recently got a 93 XJ 4.0. Slowly been fixing it up. When I first got it it had really bad gas mileage (getting like 160 m.i a tank) and would bog down when you tried to hold it on limiter and would cause it to shut off sometimes .So first thing I did was do a tune-up, spark plugs ,wires, oil change. And it was showing two codes for throttle positioning sensor and O2 sensor so I changed them. Got rid of both the codes and seemed to run better but did not fix my limiter issue and mileage is still subpar. It will rev out all day. Drive fine. It still smells rich but when you try and bounce it off the limiter if you're stuck or trying to climb a hill it will bog down and if you just keep holding your foot on the gas it will just die. Any suggestions of what I should be looking for next?

 

I think you implied you have used a suitable code reader for OBD1, or perhaps the "key trick" so it has now no codes ?

will edit in a link to the "Drivetrain Diagnostic Manual" (for OBD1 XJ)

As to "bouncing it off the limiter" I can state categorically I would cease to do that under any circumstances that weren't life or death. Call me a *****, whatever, I don't care

 

If you're talking about the rev(rpm) limiter of course it "bogs", that's how it's supposed to work. It shuts off the fuel or ignition, I forget which at the moment. It's not some sort of max rpm cruise control.

Sounds like it's working fine.
(If you think it bogs now wait until the 32year old piston runs into the 32year old valve that's closed by the 32 year old valve spring)

 

Next you should look for a new motor to have on deck, for when you blow up your existing one. 😂

 

:spits coffee:

 

It's got a reman motor from Titan in it. That's only got roughly 70,000 mi. But when you rev it up to 5200 RPM if you tried to hold it there normally it would just bounce off but it will go there once and then it will start bogging down to like four grand three grand. Sounds like it's stuttering I wouldn't say backfiring but bogging down.
​​​​​​ if you just leave your foot on the floor eventually the motor will just die. but it will start right back up and keep going

 

Never a bad idea
😂. It's a trail rig. I'm sure it's bound to happen at some point

 

The engine maxes out around 4750 rpm for hp and I think the redline is around 5200. Why are you revving it that high? As Exasemech says, the ECU cuts the fuel at full throttle. This is intend to help clear a flooded engine.