4.0 won't start.....PLEASE HELP !!!!!(Somewhat Long)

96 XJ 4.0 96,000 miles all stock. I was driving home at highway speeds and the engine started to miss a little bit. It would sputter then clear,sputter then clear???? It went like this for about a mile then died. I attempted to restart it but it would not spark. I towed it home the next morning and began searching the website for any information I could find. Here is what I have done. I replaced the Crankshaft position sensor and it fired right up for about 15 seconds then started running real rough and died. I then checked the fuel filter, looked like the original so I replaced it. Started right up and ran like a champ,(in the driveway). This morning I drive down the road about 1/4 mile and it started to sputter again and then died. I turned the key and it started right up? I headed out towards the highway and about 8 miles down it started to sputter then clear again. It finally died about 15 miles down the road. After a tow home again, I let it sit for awhile and when I turned the key again, it fired right up, not even a sputter?????? I pulled it into the garage and shut it off. I tried starting it again and it ran real rough for about 15 seconds then klunk. There was some pretty nasty black juice under the tailpipe on my garage floor that was puked from the exhaust system after the last episode. Now I get nothing. Engine cranks but no fire????? The fuel pump seems to be working fine. Cap, rotor and plug wires all look good but I don't know how long they have been on there. The vehicle was my dad's and I inherited it a few years back and brought it from Michigan to Texas. Sorry for the long post but I am stumped. Oh I now get a code 12 and 42 when I do the self diagnostics? Any suggestions where to turn next?

I'm not sure on the codes, but it sounds like a clogged cat is a possibility. Take a look at it, if its all rusty and crumbling, there is a chance it's like that on the inside, as well. I know that'll stop it up for sure.
Someone should chime in on the codes shortly.

You said the fuel pump seems to be workin fine? I would certaily verify that with a pressure gauge. Also it could very well be the coil.

OBD codes say ASD relay circuit.

Don't know what an ASD relay ciruit is, but when I googled it, it also came up to a page that said:

Error Code 42:

ASD Relay Circuit
Fuel Pump Relay Circuit


might check that fuel pressure

Thanks for the info guys...I left it sit overnight out of anger and this afternoon I went out and turned the key and did not hear the fuel pump cycle. After jiggling(thats a technical term) the wires going into the fuel pump , I went and turned the key over and the fuel pump cycled. I guess I'll be replacing a fuel pump Saturday.