Since pretty much all gasolines sold today have healthy amounts of fuel injector cleaning additives added, I really (!) doubt your fuel system or fuel injectors are dirty and need cleaning.
As bluvikng suggested, I'd change your spark plugs but with your engine's mileage I'd also install a set of new ignition wires. Just make sure to avoid those gimmicky "performance" or "low-resistance" ignition wire sets as they don't improve the TJ's engine performance but they do cause noise on your radio. Plus most of them are manufactured with no thought to longevity so the next time you change plugs, they pull apart and can't be put back together again. Your best bet is the ignition wiring set sold by the local Jeep dealer as they are excellent quality that are made so they don't cause ignition noise in your radio.
Good luck, probably nothing more than a bad sparkplug or perhaps one of the ignition wires is breaking down and allowing the spark to perhaps jump through the insulation to the block or another spark plug wire.