Probably not usually. For an idler pulley to put so much drag on the belt system that it stalls the engine, it would break or throw the belt altogether before the engine could actually stall.
Engine not getting enough fuel...dirty injectors, dirty fuel filter,dirty air filter or not enough fuel pressure (bad fuel pump).A sticking Idle speed control valve.
Your car backfires when you need a new transmission,or tune up. How do you know the difference? Simple...if your car backfires then wont start, or wont start and then backfires,you need a...