please help guys

[bugaboo1]

i have a 5.9L in my 02 ram. it is winter around december it just wouldnt start one day, i replaced the iac and it fixed the problem for 2 weeks. had it hauled to a dodge dealership and they said it was the iac and battery. had them replaced and 2 months later the same thing happend. just had it hauled to the shop and they cant find anything wrong because it keeps starting for them, i am so confused. When it cranks its acts like it wants to start and doesnt, almost like a misfire. I can definatly smell fuel after cranking on it for a while so i am guessing at the time of no start there is no spark. But why would it start a day later after that. When it runs it runs great. So far there has been a new battery,iac and i had them put on a cranshaft positioning sensor yesterday just to see if that was it. If it happens to not start again what could it be. thanks in advance.