When I put the keys in the ignition the check engine like will automatically come up, the car refuses to start while its on, eventually the car will make a noise and the check engine light will click off and the car will then start and run perfectly, sometimes this only takes a second while other times the car will sit there for up to 15 minutes with the light on until it finally turns off, any ideas of what this might be? or what I can do to fix it?