Hey everyone, I'm new to this forum and new to owning a XJ. I told my wife I would do all my own work on the jeep when I bought it but I've been having a problem and can't figure it out, I'm tired of replacing parts and my XJ budget is about exhausted.

Here's the problem. I have a '91 4.0l inline 6 XJ. After the XJ gets warmed up from driving I start having problems. After stopping and trying to go again when I press down the gas pedal the jeep almost dies unless I let off the gas. It sometime does this when I just let off the gas to slow down then try and speed up again. If I park the jeep for a while after driving around the jeep won't start unless I floor the gas pedal.

Things I've done to try and fix the problem: I've replaced the TPS, and the IAC. I put in new plugs, distributer cap and roter and new fuel filter.

The next thing I was going to try and replace the CPS but that looks like a bastard to get too. Could it be a vacuum leak?

Any ideas?

 

Probably not the CPS if you have consistent spark.
Possibly a vacuum leak- grab a can of carb cleaner and start spraying gaskets, lines, etc.. Also would be good to verify your fuel pressure.
Does it smell like it's flooding or running rich? Flooring the pedal while starting cuts off the injectors to clear a flood. That might be a direction to investigate.

 

I'm at the mechanic now because the Jeep kept dying on me while trying to go after stopped at a light. They can't figure it out yet and its been 2 hours. They checked the fuel pressure and said it was good but I asked what it read and they said it held around 40 both driving and parked and held good after shut off. I thought it should be around 55?

The mechanic said something is causing the engine to flood. He said the crank position sensor and the TPS checked good. He can't find a vacuum leak. He tried putting in a new coil thinking it was bad but the jeep had the same problems.

Now he's going to work on another car to "clear his head"?

 

The mechanic couldn't figure it out so I have to take it somewhere else.

 

It seems that way. MAP sensor + vacuum tubing might be an issue for your year, shorts in the injector wiring harness aren't uncommon, worn out or sticky injectors..
The injector plugs should have +12V on one pin, the other pin is switched to ground by the PCM to open the injector. You can do a rough test by measuring the voltage across the injector plugs one by one with the engine running. They should all be the same. If one reads higher, it's likely spending more time grounded. A NOID light might work too.

 

Could be the the coolant sensor in the thermostat housing. If it's bad it could be telling the ecu to add more fuel flooding the motor out which would explain why It runs fine until it warms up.

 

It does kinda sound like it's in open loop yet after it's warmed up....

 

Does your check engine light come on? I'm having the same issue and my light came on. the code said that the fault was a MAP sensor.

I haven't had time to deal with it, so I'm running a higher grade of gasoline which seems to have fixed it for now. Try that since gas prices are down!

Where do you live? I have this issue every winter when it falls below 20 degrees.