2.2 chevy cavalier not starting

working on 2002 chevy cavalier 2.2 was missing firing i was thinking it was one of the coils i switch around the coils now it wont start. i check the firing order many time still nothing. it back fire through the oil cap and blew it off. i was wonder did the time belt/chain skip or breack.? i look up the firing order to coils on google says i have it right. idk whats going on. never had problem like this before. please someone help