Engine Performance problem
1999 Jeep Cherokee 4 cyl Four Wheel Drive Manual 42000 miles

I just bought a 4th hand Jeep Cherokee, it ran great until the other day when it started losing power and sputtering and backfiring when pressing the accelerator. I shifted gears without accellerating and it went ok but as soon as the accellerator was pushed it sputtered and backfired and bogged down. Then later after it sat, a bit, restarted it and had no problems, then later it did it again. What could be the problem?