Di Luigi finished a bruising 19-play opening drive with a three-yard touchdown run as the Cougars (2-4, 1-1 Mountain West) snapped a four-game losing streak. The last time BYU lost five in a row in a single season was 1970.
Ryan Lindley threw for 220 yards and three touchdowns for San Diego State (3-2, 0-1), which came into the game ranked 24th in the nation in rushing.
BYU beat the Aztecs at their own game, holding San Diego State to minus-2 yards rushing in the first half and 53 for the game.
Kariya scored on a two-yard run late in the first quarter and a one-yard burst early in the fourth quarter to give BYU a 24-14 lead.