The contest was tied with 12:51 remaining, but the Cardinals ended the game on a 31-16 surge.
Dieng made all eight of his attempts from the foul line while Gene Teague was adding 14 points and 10 rebounds. Fuquan Edwin contributed 13 points for Louisville (14-1, 2-0 Big East Conference).
Brandon Mobley scored 18 points for the Pirates (12-4, 1-2), who have lost two in a row after winning seven straight.
Beautician charged with giving client fatal silicone butt injection
LGBT community has 'bullied the American people': Bachmann