I have posted this same problem earlier this week but under a different title and now I have more info as to troubleshooting. It is a 2000 XJ Sport 4.0L, and it will sputter and then die like I just ran out of fuel, but only after I have been going up a mountain for several miles. It will not start up right after but if I pop the hood and let it sit for about 10-15 min it starts right up and keeps going for a little while. I have noticed that it dies about when the engine temp gauge goes just past the 200 degree mark. When I am going uphill I am not exceeding 3000 rpm and I am not flooring the gas pedal, simply feathering it like normal driving. I do not believe altitude has a direct influence on it because the second time this happened I was able to reach the summit and ended up spending the rest of the day there wheeling/mudding with no problems. I have checked the fuel pressure, replaced the Idle Air Control sensor as well as the Camshaft Position sensor (both from Auto Zone, which may be where the problem is coming from). I have taken it to a couple of parts stores to pull codes on two different occasions resulting 4 different codes. P1391, P0100, P0400, and P0090.

 

My WAG is temperature, not fuel, as the main cause. Going up hills like we have really increases the temp.

Have you Googled the codes? You'll get a lot of ideas.

 

I did google them and they are completely random. I got a Mass Airflow sensor, exhaust recirculation, and a fuel pressure regulator. The code I got from the very first time turned me towards the Camshaft Position sensor and the Idle Air Control valve.

 

Does that also happen when you are not climbing a hill? If so, time for the hair dryer test.

 

Nope, around town and on the freeways it does just fine with no problems, it is only when I am going up a long road/up a mountain.

 

"I have taken it to a couple of parts stores to pull codes on two different occasions"

Erase the codes and start from scratch. Is the overall condition of the vehicle wiring poor?

 

P0090, P0100, and P0400 don't exist for a 2000 XJ 4.0.

P1391 is Intermittent loss of CMP or CKP (CPS).

Possible causes for 1391:

CMP SENSOR OUT OF SYNC
DAMAGED TONE WHEEL/FLEX PLATE (CRANKSHAFT)
DAMAGED TONE WHEEL/PULSE RING (CAMSHAFT)
IRREGULAR LAB SCOPE PATTERN OF CMP SIGNAL
INTERMITTENT CKP SIGNAL LOSS WHEN WIRING IS WIGGLED
IRREGULAR LAB SCOPE PATTERN OF CKP SIGNAL
WIRING HARNESS INTERMITTENT
INTERMITTENT CMP SIGNAL LOSS WHEN WIRING IS WIGGLED
SENSOR CONNECTOR/WIRING
SENSOR CONNECTOR/WIRING
CAMSHAFT POSITION SENSOR
CKP SENSOR CONNECTOR/WIRING

CRANKSHAFT POSITION SENSOR

I see you already changed the CMP.

Examine wiring.

Possible bad CKP/CPS(?)

 

It ended uo being a bad CRANKSHAFT and CAMSHAFT sensor. I went cheap and got the first one from auto zone. The second one I went and got mopar and that solved the issue.

 

Sure see alot of that, don't we?

WunHungLo and his buddies supplying crappo parts.