Oil cap is there to close off the crankcase--keep in oil--Keep dirt out--let the PCV system operate as it was meant to.
I really do not think it affected your engine at all, You do need to put it back on!
I think maybe you need to perform a tune up, for your engine's performance
If your check engine light is on, take it to a Popular Auto Parts Store. Normally they can read your codes for free. Light on, means there is a problem with you vehicle, and needs some attention.
You can return here with any code numbers, someone here, can steer you towards what needs attention.
Thursday, May 26th, 2011 AT 2:40 AM