To clean the fuel injectors in a Lincoln Mark, you can use a fuel injector cleaning solution specifically designed for gasoline engines. Start by adding the recommended amount of cleaning solution to a full tank of fuel. Drive the vehicle for a significant distance to allow the cleaning solution to circulate through the fuel system and injectors. This process helps remove deposits and improve fuel injector performance. For more severe cases of clogged or malfunctioning injectors, professional cleaning or replacement may be necessary.