1990 and 1996 - he was incredible and the team was awful.
That said, you could easily make the argument that he kept numerous horrible teams from being horrible instead of in the mediocre/average range. The same is true of Peyton Manning: The Colts were 12-4, 14-2, 10-6, and then Manning couldn't play in 2011: They went 2-14. Perhaps his performance was frequently just superb within an otherwise dreadful team.