Van Horn, who tipped a missed shot by Andre Miller back to himself in the lane, was perfect again, with the ball sailing cleanly threw the net at the buzzer.
Van Horn's shot came only a few feet out from the same basket where he tipped in Miller's lob pass at the buzzer a night earlier to beat Southern Methodist.
And it came after a dreadful night for the 6-foot-10 All America candidate, who had only eight points before making the winning shot.
Utah (25-3) advanced to Saturday's final against Texas Christian.
If not for a traveling call on New Mexico's Kenny Thomas with 34 seconds left, Van Horn might not have had a chance for his second night of heroics.
Thomas had the ball and a clear path to the basket when he traveled. Utah then played for the last shot, with Miller driving the land with just a few seconds left.
His shot bounced off the rim and Van Horn tipped it to keep it alive, then grabbed it and went up with the winning jumper.
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