Yesterday no problems. This moning dead battery, barely enough to turn little red light on by key. Tried jumper box, enough to turn over a couple turns a let out a HUGE backfire. Got a new battery, no problems for about 2 hours. Startin popping a few times at one job, finished no problem. Next job stats fine, when you put any load or move the throttle up fast pops and hesitates. 13.86 volts at the battry running. 12.6 right now sitting. Any ideas where to start? Bad coil that shorted out possibly? Thanks for any help.