Argentinean striker Pacheco's dominant performance inspired Juan Aurich to a comprehensive 4-1 victory over the out-of-form Inti Gas, who conceded four goals for the second week running in the Apertura on Sunday.
Juan Aurich made a dream start, when Pacheco fired the ball into the back of the net after just one minute at the Estadio Elias Aguirre.
It got better in the 19th minute with Pacheco on target again, while Hernan Rengifo struck five minutes later to heap further misery on the visitors.
Francesco Recalde pulled a goal back for Inti Gas nine minutes into the second half, though Pacheco restored the home side's lead with his third of the match in the 73rd minute.
The win, and Melgar's shock 1-0 loss against San Simon on Saturday, lifted Juan Aurich to the summit after 13 rounds in Peru.
Juan Aurich are level on 24 points with Universitario but ahead due to their superior goal difference, while Melgar dropped a point off the pace.
Universitario left it late as they overcame Cesar Vallejo 2-1.
Edison Flores' 89th-minute solo effort from the halfway line saw Universitario win at Estadio Mansiche on Saturday.
Scores were level with five minutes remaining after Cesar Vallejo's Daniel Chavez cancelled out Cris Martinez's 58th-minute opener.
However, the visiting side walked away with all three points thanks to Flores, who received the ball on halfway and drove towards the penalty area before beating Salomon Libman at his near post.
In other results, Universidad San Martin accounted for Real Garcilaso 2-0 courtesy of Santiago Silva's first-half brace on Saturday.
There were four goals scored at the Estadio Alejandro Villanueva as Alianza Lima and Union Comercio played out a 2-2 draw.
Cienciano and Sporting Cristal also shared the spoils, drawing 1-1, while Sport Huancayo picked up a convincing 5-1 win over fellow strugglers Los Caimanes in Monday's final game.