My 1996 (Vortec 350) had been misfiring out of the blue and barely even running, well we let the truck sit for about a week because i didn't have the time or the money to mess with it. So when i went to try and find out what's wrong it wont even fire up now. I replaced the icm because it was $25 and wasn't gonna hurt to replace it then tried to start it and it pops like it wants to start but it sounds like it's sparking to early. Any help is appreciated because I'm uncertain of what could be wrong. 