i am 17 and i just swaped my motor myself and now i am having a miss fire that just keeps getting worse every time i drive it. its pretty much when im leaving a complete stop slowly and when im in low rpm while driving. also when i turn the truck on no codes or lights come on, but once i drive it a little the "check engine light" comes on, and it also wont pass emmisions. i am tryin to get it running decent because im movin to college at UTI in a week and i dont want to have any problems with it. any information would be great! i do have very old gas in it as well which could be part of it what should i do?