First of all last week it started to buck and seemed like it was miss firing so I replaced it's plugs. It ran great for the first 2 days after that and then started to act the same way. So I thought bad gas, so I changed out filter and checked everything I could think of. But still sputtered and back fired. And now today it acted like it wasn't going to start when I left for work. When I got off I had to crank it a few moments before it started. But once I got it home and tryed to start it again that was it, Just clicks. Thought it was my battery so I hooked up my charger and it says the battery is full. Lights seem bright but the check engine light is still on. Can some help me?