Help! 1998 Jeep wrangler is missing.

Hi, I have a 1998 jeep wrangler and I need your help in solving a problem! I recently took it to a machanic because it was missing and backfiring badly. He changed all the wires, plugs, rotor, and distributor cap but it didn't help, it's still doing the same thing. It doesn't seem to matter if its a damp or dry day, and once it acts up and sits for a while it seems to run fine again. I'd appreciate any suggestions? Thanks a bunch!

Maybe crank position sensor or camshaft position sensor? It's a 4.0 Liter, right?

I agree with Jackson. I haven't had this problem with my Jeep but I did have the exact same problems with a 91 Grand Am. I would definately check out the crank shaft sensor. With the Grand Am it would run fine for several miles and then just die. If I started it up right away it would run for several more miles and then die again. If I let it set after driving 10- 15 minutes it wouldn't start. Had to let it set at least 3-4 hours before it would start and sometimes several hours were required. I sank alot of money into new computer and had it at 4 yes 4 mechanics and on various computers and they couldn't find the problem. I hope this helps. Good Luck.

I had a similar problem on my 1995. I replaced the crank sensor because everyone has had problems with them, but it turned out to be a bad fuel pump relay. I found a small crack on the side of the relay and found the inside to be corroded. I haven't had a problem since