Saturn Ion dies when gas cap is removed.

I read about the Onboard Emmissions control system sometimes actually causing such wierdness. Apparently, it is so freaking sinsative about getting you the best mileage and protecting the air we breath that it is easily upset. Try rreading the manual about your OB(?) Forgot the third letter. Or, sign up to Alldata. It isn;t free but if you can't find free help, it is worth it. Mike