xj get up to temp and dies!!!!

Hello, New to the site and just bought a 91 xj 4.0 HO auto 4x4. 200k on the motor but she just purrrrz and has plenty of power. The problem i am having is when the motor gets up to 210 degrees or operating temp it will die and you have to wait a few mins before it will start and you can travel untill it does it again. when its about to die if you mash the gas to the floor it will go again only for little though. Guy i bought it from has replaced the fuel pump and CPS. I positive of this. and he did a fuel filter as well. any suggestions on this would be great the other problem is the front axle will not engauge. the transfer case works just not 4x4. any help on these???? thanks. I have searched the forums but not found same symptom.

sounds like the CPS to me, get one from the dealer instead of the cheapie stores. (I just had a friend's 96 do the same thing - he bought two bad CPS from Advance Auto Parts, spent $1500 in taking it to various shops around town; including dealer, then bought a CPS from the dealer - runs fine)

check where the axle connects to the vacuum lines if it's a vacuum system, you may have a leak or a hose off

well i found the 4x4 problem. all the line fell onto the exhaust awhile ago i guess. all four vac lines melted together. how should i fix? soft rubber splice or?i know two go up front and the other two go up to the tank. gonna be fun.
as for my dieing issue itook TB off and cleaned that and the intake air temp sensor, put dielec grease on every connector i could find cleaned and made sure the ground strap was good and put new conectors on the ballast resistor thing . while under the xj i was looking at the exhaust and right were the ox sensor is just below it the exhaust pipe is right against the oil pan. is this normal? gonna test it out more on the way to work tonight if it fails on me again i will go get a CPS from dealer tomorrow any feedback would be great. thanks

Are you saying the exhaust pipe is too close to the oil pan, or the wire from the O2 sensor is too close to the exhaust pipe?

I ask because this might affect your problem. When the engine is cold, the ECU operates in "open loop" mode. It does NOT use data from the sensors, it runs on a slightly over-rich pre-programmed fuel map. When it gets up to normal operating temperature it switches over to "closed loop" mode and then uses data from various sensors (including the O2 sensor) to control the air-fuel mixture.

If your O2 sensor wire(s) is/are shorted out, then I suppose it might run when it doesn't need that data but it couldn't run when it's calling for that data because the data won't be available.

to clear it up. the exhaust pipe is right against the oil pan. this is adding heat to the oil i'm sure. can a new down pipe be purchased or after market larger diameter?

ok today i pulled codes and it came up with a 76 fuel resistor bypass relay circuit. where would this be located? no other codes popped up but i did ohm and volt test on all sensors MAP, MAT, CTS as well as the new CPS all failed. All mesured at operating temp.
grrrrrrr! can this be? could the computer be shot? help.

fixed the code 76. It was a broken wire on the ballast resistor relay( red wire blue strip) and now the fuel pump is very quiet. but did not fix the stalling issue. so we had an extra coil a buddy gave to me to try and we put that on and whallaaa! we drove for a soild 45 mins in hot weather, was still warm from on test runs before. She did not stall once. But the fuel pump began to get noisy towards the end of the run. But I have been told that after market pumps are just loud and it may have been hot from running on the highway. so all seems well in the electrical side on things now to fix the vac lines for the four wheel drive front axle. any ideas on how to splice them back together? And the rear end is alittle loud. kinda grumble sound under acceleration. any ideas on this? 212k
could need a bearing or somthing. hope this may help others and looking forward to others to chime in on my next hurdles. Thanks for all the previous help...

Depending on the sound it makes, for the acceleration grumble, check the driveshaft universal joints and also check for loose or misaligned exhaust. I've had universals go bad without play that can be felt, so if their history is uncertain, it might be worthwhile even if it isn't loose, to disconnect the joint at the rear, and check the cups for stiffness. It's probably a good idea to check the rear wheel bearings too. A little end play is normal, but they should be quiet, and not have any side play. That's if it's a rumbling sort of grumble. If it's more of a whine, it could just be noisy gears. Probably worth checking the condition of the fluid, and perhaps throwing in some synthetic lube, but at that age a noisy rear end isn't that unusual, and it can whine for years to come without getting much worse.

89xjayed said:

so all seems well in the electrical side on things now to fix the vac lines for the four wheel drive front axle. any ideas on how to splice them back together?

Click to expand...

I've got a complete vac harness, somewhere in my mess of parts, if you want to replace it with OEM. PM me if you'd be interested....
Jeff

Glad you found the problem.

I was going to suggest that you check out the 02 sensor.

I had a Ford Taurus do this (and I will never have another Ford as a result).
It would die, right in the middle of my commute, and only when the
engine was good and hot. Towing charges were killing me, not to mention the inconvienience.
Spent $1400 changing fuel injectors, fuel filters, etc.
Most mechanics never drove it long enough to have it heat up to the point of failure, so they just gave up.
One mechanic put the computer on it, and the O2 sensor had failed.
He replaced this one part, and the engine came back to normal.
$15 part.