Detroit (5-2) was missing three rotation members - Kentavious Caldwell-Pope, Brandon Jennings and Jodie Meeks - while the Sixers (2-6) used a rag-tag roster in the final preseason game for both teams.
The Pistons led 58-57 after a first half that was played without much defensive intensity. Detroit shot 53.8 percent, and Philadelphia hit 52.8 percent of its shots.
Detroit led by as many as 13 in the third, but couldn't put away an inexperienced group of Philadelphia reserves.
The Sixers led 93-91 with 4 minutes left, but a Smith 3-pointer with 90 seconds broke a 99-99 tie, and the Pistons held on to win.