i seem to have a very similar problem. I am attempting to drive around without the gas cap and then putting it back on but it doesnt seem to work. Perhaps you did it a certain way? Did you unscrew the gas cap while the car was still running? Did you screw it back on while the car was running or you turned it on/off between !Removed! the gas cap back in.
Please try to be specific so i can try it out for myself and see if that solves my problem