I have a question about the engine in my car. It was working perfectly while i was sitting in my driveway, then i turned it off, went inside for a bit, and came back out to go to walmart. It wouldn't start and it kept turning over and then finally started for a bit, but was really rough whenever i pressed on the gas, then when i let off it died. i think i heard a big bang and a bit of smoke came from under the hood. now it just turns over and every once and a while the exhaust will backfire and sounds like a paintball gun. I dont know what could be causing the problems. A timing chain? Fuel Filter? I know it's not the air filter but I can't think of anything that could happen all of a sudden like that. Any help you guys have would be awesome.