runs rough, now won't start

[BPB]

My 90 xj 4.0 has been having a problem were when i start it some times it runs realy rough, like it is not firing on all cilinders, then I would turn it off and let it sit for a minit or so then it runs fine yesterday I started it after sitting for a few days, it ran rough, the i turned it off and let it sit for a while like normal, then it wouldn't fire up. what could this be, could it be a fouled plug??
it is sitting at a house that I have been working on and I need to get it home, please help!!!!!!

[Dr. Dyno]

As always, when an engine won't start we go back to basic principles to try to find out the cause.
An engine needs fuel, air, and spark to start and run. Unless your air intake is obstructed or your air filter is severely clogged up, your engine should be getting air. That leaves the fuel and the spark.
To see if it's getting fuel, take the cap off the Schrader valve on the injector rail (looks like a tire valve), press the valve in (have a cloth rag ready to catch the fuel, and ask a buddy to crank the engine. If the fuel pressure's within spec, the fuel should spurt high in the air like a fountain. If it's only a trickle, there's a problem e.g. severely clogged fuel filter, kinked/blocked fuel line, bad fuel pump.
For spark, check if there's a spark coming from the coil lead to the distributor (wear gloves because a 30,000v shock through the arm isn't very pleasant). If not, it could be a bad coil or a bad CPS. The Haynes manual describes how you can test the CPS. If there IS a spark there, the problem could be downstream e.g. worn dist. cap, rotor, plug wires, plugs.

[XJ_ranger]

also check and see if a new TPS (Throttle Position Sensor) would help. When mine went, i had similar problems.

wouldnt start, when it did - rough idle combined with rough acceleration...

fun times
-Ranger