Ok today i was startin up my car to go home from school and poof a big bluish kinda cloud came out my exhaust. Later when i got it home and started it up after it had been sitting to see if it would do it again. It did this time with a very bad smell and there was a little smoke comming out of the passenger side pipe constantly. Also my car has been dying out of no where at stop lights, signs, whenever i have to come to a stop is when it happens. It has happend 3 times in the past week and its really starting to annoy me. The car doesnt sputter or anything it just dies without warning. Cat has also been popping for some reason...maybe unburned fuel. Dont know where to start on any of this. Please help!!! I need suggestions!!!

 

blueish smoke = oil

since it's smoke on startup it is most likely your valve seals.
if it happens while you're driving too then it is possibly your piston rings.

If you car is just dieing, and not sputtering, while you're at a stop light, you might want to check your belts, an extremely loose belt around the alternator could cause that. No sputtering when dieing is normally electrically related. I'd also have your ignition module checked 1st thing. It could leave you stranded somewhere.