1996 Grand Cherokee Jeep backfires?

my 1996 Grand Cherokee Jeep starts cutting our badly then backfires even if your driving at a high speed, slow or even stopped. some days it may do it just once a day and not again for two or three days, other times several times in one day. We changed out the fuel filter being told that would fix it, didnt work. does any one know what it could be? fuel pump seems to be working ok so im clueless !!