Driving with oil cap off

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.

The Medic

I feel sure you have more than one O2 sensor, did the code pin down which one needs attention?

Never heard 'em say don't buy the part---they having problems with them?

If your O2 is down, your vehicle runs in "closed loop" which is inefficient (MPG goes down, etc.)

He give any reason why?

The Medic