When you fill the gas up the car runs rough?

If your car runs rough after filling up with gas, it could be due to a few factors. One possibility is that dirt or sediment from the gas tank was stirred up during refueling, contaminating the fuel system. Another reason could be a malfunctioning fuel injector or issues with the spark plugs. It's also possible that the new fuel has a different octane rating than what your engine is designed for, leading to poor performance.