engine trouble cranks but no fire

i have a 98 civic 4d lx and recently the muffler system fell off. and it started fine even with it off....but now i let it sit for maybe a day or 2 and now it doesnt want to start......it cranks but it doesnt fire. i thought maybe it was cause the engine was cold and there wasnt enough back pressure to suck the exhaust im wondering is it because the exhaust is gone that it is not starting? plz hlp.....thx

ignition coils? when your ignition coils go out, your car will turn over but not start completely. just a guess.