Engine shuts off when decelerating, backfires, now will not start

Okay, used to start real easy but now it does not start. It just turns over over and over and over. Over morning desk crank it's spitting and sputtering and cutting out misfire and backfiring. It stalls on me when I'm going down the road it stalls on me and quits every time I slow down to make a turn or to make it stop. I have put two oxygen sensors on it that's what the OBM called for and then reset it and now it cost for another idle air sensor which I haven't put on it yet. I put a fuel pump on it yesterday it cranked up just fine run perfect down the road and back turn it off and back on two or three times it crank great and then shut it off for 5 minutes. Went back in the house come back out and crank tried to crank it and it wouldn't crank up doing the same thing it was doing before.