1994 Jeep Cherokee Jeep will shutoff while driving

Hi,
I have a 1994 Jeep Cherokee with a 4.0 ltr with about 212,000 miles that just shutoff on me while driving the other day. I had the fuel pressure checked and I was told it is fine at about 45psi. I then checked the ignition coil for spark and found none, so I replaced it and the rotor and that seemed to solve my problem for about a day or two. It then shutoff on me again and I took it back to the mechanic and he replaced the crankshaft sensor and the magnetic pickup inside the distributor. That also worked for about a day or two, but now it is worse than before and I, frankly, am stumped. What else could be preventing it from running properly. The computer does not give any codes and the check engine light did not turn on. It was suggested that I take it to an automotive electronic shop to see if they can help, but I can't get it to run long enough to drive it anywhere. I was also told that it could be the distributor or the wiring to the auto shutdown relay. It had been running great for the past six years (as long as I have had it) with proper maintenance. PLEASE HELP.