Sorry if this is an already answered question - I looked around a little bit before posting this and didn't find anything directly answering it:

I drive a 2wd automatic 99 XJ (wish I could have found a 4wd stick) that I recently lifted and added some weight (swing back bumper, roof rack, tires) to. Lately when I run my Xj for a bit (30 mins at 60 + mph or 1.5 hrs closer to 50-60 mph) the engine sort of just quits on me - I feel a small pump from the engine as if it were shifting gears and then the engine dies. Electrical stays just fine, however I can no longer accelerate and pushing down the gas pedal does nothing. Stopping and attempting re-ignition right away yields somewhat of a dirty or bad start or an attempted start that sounds nasty and quits halfway through.

Initially I thought it was an overheating issue - a radiator flush showed that I was having blockage to flow - however, while replacing the radiator did help how the Xj runs, it didn't permanently solve the issue.

Usually if I let the XJ sit or cool for about 10-30 mins the XJ is good to start up again and finish the commute home.

I think it's a heating issue unrelated to the cooling system - maybe the extra weight caused the jeep to work a little harder, generating more heat, which messes with some of the sensors or electrical equipment, but don't have the experience to know what to test or look for.

Either way I could be wrong.

Does anyone have any experience or tips with this issue?

Many thanks ahead of time.

 

Did your temp gauge show overheat? Is the coolant overflow bottle venting steam?

 

Faulty crank shaft sensors cause the problems you're having.
Don't just take my word for it. Have it checked.

 

Again I say... not very scientifically.... put on a glove. Start the engine. Grab a wiring harness... shake.
Grab a plug connector.... shake.

You can find gremlins. If it dies when you do something. You found it.

Cheap, easy, not very scientific, but can be done tonight, with no tools.

 

i doubt that very very much.

 

The extra stuff bolted on DOES make the engine work harder, but the cooling system can handle that.

Maybe you are having a fuel injector issue? With heat coming up from below?
People talk about this problem in some XJs - without a heat shield protecting the injectors, heat comes up from the exhaust and vaporizes the fuel in the fuel rail before it gets to the injectors.

But that problem usually shows up when you turn the engine OFF, and it won't restart. It doesn't die while driving...