xj wont stay running

I have a 1991 xj 4.0 liter inline 6 it would run fine as long as it was sitting and idling but when we took it up the road about 3 miles it shut off and wont start back. I have replaced the plugs and wires, distributor cap and rotor button and the fuel filter and still nothing any suggestions. thanks

Does it turn over? Fuel filter maybe?

Lots of suggestions, but tough to make an accurate call without more information. Could be pretty much anything spark or fuel delivery related from a loose/bad CPS, ECU failure, debris in the fuel tank, dead fuel pump, are just a few things that come immediately to mind.

Take it step by step. Isolate the problem. Lack of fuel, or spark @ the cylinder? Pull a plug and turn the engine over to check it's getting spark. Check the fuel pressure @ the rail to make sure fuel's getting to the injectors, and go from there.

The alternative method to step by step diagnosing, is the "throw parts at it" approach. Which eventually works as well, but is sometimes an order of magnitude more expensive.