For the last couple weeks I have noticed a change in my idle. When I start it up, it seems fine, but a few minutes later it revs up to like 2500rpm's and drops to like 500 rpms in an instant and my check engine light comes on and then goes back to it's normal idle with no check engine light on within a few seconds. Does anyone know what the problem could be? I know something has to be wrong but I am not sure what. Can someone try to point me in the right direction? Thanks for all your help!