When I fill the gas tank the vehicle does not start correctly. It acts like it is getting to much fuel when it starts as though it is flooding. Sometimes it will die before the idle smooths out. When that happens it is difficult to start. It acts like it is getting too much fuel. It did display a code that the a local mechanic advised showed a rich fuel mixture. It only has difficulty when you fill the gas tank. This vehicle does not have a gas cap, only a gas lid. The mechanic suggested that since I drive a lot of gravel roads, the filler neck needed cleaned and lubed to seal the lid. He performed the repair and the vehicle still had difficulty starting on fill up. Any suggestions.