What the heck???

hey my first post . Ok here's the problem, I'll start my car when it's cold and 5 mins later it will just cut out. I checked to see if there was a spark and there was none. So i left it for a couple of hours and came back to try it, and it started right up. Then cut out again(no spark). Ive changed the ignition switch, Blue temp sender, coil, cap, rotor and still nothing. Iam thinking maybe the ecu but i don't want to buy one if it's not the problem. Any help would be appreciated