An ion sensor glow plug assembly includes a metal shell for attachment to a cylinder head of a compression ignition engine. The ion sensor glow plug assembly also includes a center terminal at least partially disposed in the metal shell and connected to a source of power to create a heating circuit. The ion sensor glow plug assembly includes a metal glow sheath disposed at least partially in the metal shell and about the center terminal. The ion sensor glow plug assembly further includes an insulator disposed about the metal glow sheath and at least partially in the metal shell and extending axially into a glow area of the metal glow sheath to clean off soot on the insulator by glowing.