The capital-based club had started the league season with a 4-0 thumping of Colo Colo but had to wait until round 13 to taste success again as they thumped Everton 4-1 to end a six-game losing streak.
Gamadiel Garcia and Felipe Mora scored in the first half for Audax Italiano before Ivan Vasquez and Juan Francisco Cornejo struck after the break to take the hosts four goals clear.
While Angel Rojas got his name on the scoresheet for Everton in the 86th minute, the visitors never had a chance to recover after Audax Italiano's powerful start and slumped to their sixth defeat in seven matches.
But Munoz came off the bench in the 78th minute and scored after four minutes on the pitch to clinch Catolica's fifth win in six games in all competitions.
Catolica moved to 30 points, while O'Higgins remain second on 27 after thrashing Cobresol 4-0 and Universidad de Chile (22 points) leapfrogged into third above Cobreloa (21) with a 3-0 victory away to Union La Calera.
