Hello, I have a 2000 w/ 4.0, auto, ~120k. I travel quite a bit for work and when the jeep sits for more than a week or so and I start it back up, it starts ok but runs very rough and backfires some during acceleration. It smooths out over the next 50 miles or so. The check engine light came on last time (this past Sunday). Will get a scan tool on it and get a code tomorrow. I replaced the computer w/ a used one, no effect - does the same thing. Has new plugs, doesn't have wires. Any ideas?

thanks.