My engine is stuttering when you go to start it and acting like it doesn't want to start. It only does it when it's really hot and it's been sitting for awhile(ex. after I get off work). It also stutters occasionally when you are driving it. My boyfriend thinks it's the fuel filter. The check engine light says there is air in the fuel delivery system. I replaced the gas cap as a possible cheap fix. What is it? Ideas????? Thanks everyone!