HELP!! 98 XJ Dies, and runs bad until cold

I have a 98 XJ Cherokee. 4.0L Automatic. I have never had a single problem out of it until now other than crappy battery connections. It runs perfect until I get down the road a few miles, then it dies. When I restart it, it doesn't want to stay running. It runs very poorly, and only can drive about 2 mph. Once it cools, or sits for about 10 minutes, it will run again for a few minutes, perfect. Then it'll do the same thing. It doesn't throw and Diagnostic Trouble Codes either.. I dont know... I cant seem to find any answers on the net!

and no answers here?

mattriddle said:

I have a 98 XJ Cherokee. 4.0L Automatic. I have never had a single problem out of it until now other than crappy battery connections. It runs perfect until I get down the road a few miles, then it dies. When I restart it, it doesn't want to stay running. It runs very poorly, and only can drive about 2 mph. Once it cools, or sits for about 10 minutes, it will run again for a few minutes, perfect. Then it'll do the same thing. It doesn't throw and Diagnostic Trouble Codes either.. I dont know... I cant seem to find any answers on the net!

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This could be way off, but, is it possible the choke is not operating properly? I'm not familiar with the 98's, but on the '91 the choke plate (top of throttle body, under large hose from airbox) should be closed when engine is off, open slightly on startup and slowly work its' way to wide open as the motor warms up. If it's staying closed it won't get enough air and stall. But that could be way off.

Sounds like a sensor issue...something is screwing up once it warms up and switches from open loop mode (PCM running fuel ignition system on pre-programmed settings) to closed loop mode, where PCm is taking input from sensors...
Sensors most suspect in my mind would be 02 sensors, as they start providing input to PCM when vehicle is warmed up...most other sensors provide input to PCM when running cold...
please remember that any sensor that goes cuckoo once the sensor itself warms up, can drive your PCM nuts also...

you can trying disconnecting 02 sensor/s and she how she runs once it warms up...
will probably run rich on fuel but should still run like the motor was cold...

plugged catalytic converter can also kill power severley...

my two cents for now...
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has the fuel filter been replaced? I'd start with a filter that's plugging up with fuel flow and the sediment is setteling when the flow stops long enough to get a little farther before it pluggs up again.

if the filter is replaced and it continues to act up, I'd look at a fuel pump failing as it heats up or CPS failing from heat.

Well there are no trouble codes, and it runs strong until it goes to running bad. I was thinking fuel pump too, but usually when a pump starts to fail, there will be power loss... I also put another ecm in it while it was acting up, and it still ran crappy. I also replaced the fuel pump relay. If it were any of the sensors, wouldnt it throw a code?

does it do it while driving, or only after sitting? I had similar issues and consensus was heat soak in #3 injector (after sitting). mine runs fine on cold days....on hot days, it barely runs after sitting.

only while driving. it could be a 1/4 mile, or 5 miles before it does it

I'd bet crank position sensor.

mattriddle said:

Well there are no trouble codes, and it runs strong until it goes to running bad. I was thinking fuel pump too, but usually when a pump starts to fail, there will be power loss... I also put another ecm in it while it was acting up, and it still ran crappy. I also replaced the fuel pump relay. If it were any of the sensors, wouldnt it throw a code?

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read through a couple of hundred driveability threads posted in this forum...more than 50% will not have a code thrown...OBD2 on your vehicle is 10 years old...the technology was not bulletproof for detecting bad sensors...

Glacialbass said:

I'd bet crank position sensor.

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yeah...seems like CPS for dying while driving, heat soak for poor running after sitting.