rough running 4.0

have a 96 cherokee 4.0, usually runs great about every 3-400 miles it'll start running rough, missing at idle speed and just wont start sometimes itll get fire to the wires sometimes not, gets good fuel pressure to the rail so far i've changed cap and rotor button plugs and wires and fuel filter all the cheap stuff but now im going to have to put either a distribter, coil, or a crankshaft position sensor on it what should i do first any help would be greatly appericiated. and any other diagnostic on it would help to im just a shade tree mechanic thanks

I've only had my Jeep for about a month now, but I have already heard numerous stories that the crank sensor is a habitual problem source and could cause symptoms like ou describe.

Crankshaft Position Sensor is where I'd start also.

Does the 3-400 miles have to be consecutive like on a road trip or otherwise? I don't have much to add except maybe there is a plug wire getting hot against the block or something. I would imagine that the wire or plug would get too hot sooner than a few hundred miles though. Do you ever see any smoke like there is a bent rod on the exhaust side or anything? Are there any engine lights on? Maybe you could connect the car to a computor to see if you get any check engine codes etc. Good luck I wish I had a deeper understanding of what to do for ya. DRIVE IT LIKE YOU STOLE IT!!!!!!!!!