1991 ford mustang wont start?

hi i have a 1991 ford mustang lx 2.3l when i first got it. it ran good just needed new plugs an wires so i replaced them an it never missed then one day it started miss fireing on cly 3 it would not burn gass on the plug. so we put two bran new coil packs on it hoping to fix it an now when cars is runing only the 4 plusg on the back coil pack will spark when u take them off. any one of the 4 plungs on the front coil pack wont spark at all. so it should be my dis as in the igintion control module an i replaced it with one from a junkyard an it tested good first try. my old one tested 5 times bad then tested ok the 6th time so the guy at autozone said my old one was bad. so i put the new dis on an it started up an sounded good but only ran for like 5 sic then it died an wont start??? i really need help if any one know something plz reply. thank you