Muncy homered for the first time since 2016, Corey Seager had four hits and three RBIs and Kenta Maeda struck out 10 for the Dodgers, who beat the San Diego Padres 13-4 Wednesday night.
The Dodgers extended their season-high winning streak to four and outscored the Padres 30-10 in the series.
Muncy, recalled from Triple-A Oklahoma City on Tuesday, hit a two-run homer to left to cap a five-run outburst with no outs in the third inning against Luis Perdomo that gave the Dodgers a 9-2 lead. Chase Utley was aboard on a two-run double that followed Joc Pederson's RBI single.
Muncy's last homer came with Oakland in 2016, when he hit two. He spent all of 2017 in Triple-A.
''It always nice to get the first of anything out of the way, whether it's your hit or home run or even a play in the field,'' said Muncy, who signed with the Dodgers as a free agent in April 2017. ''It kind of gets the butterflies out of your stomach and jitters gone.''
The Dodgers' offense is ''pretty impressive,'' he said. ''It's fun to be a part of it.''
Said manager Dave Roberts: ''When you're scoring the runs we are and we're stressing their pitcher, our pitchers are attacking guys. When we're on the offensive, getting guys on base, running the bases well, it just breeds energy. The energy goes to another level and we play our best.''
The Padres struck out 13 times. On Tuesday night, they struck out 20 times in a 7-3, 12-inning loss, tying the club record set in a 15-inning game in 2001.
Maeda (2-1) allowed four runs and eight hits over 5 2/3 innings, his longest outing of the season. He matched the 10 strikeouts he had in his first start, a win against San Francisco on March 31. He walked two.
Maeda walked Austin Hedges with the bases loaded in the second, then allowed Perdomo's sacrifice fly. He allowed Carlos Asuaje's two-run double in the third.
The Dodgers scored three runs in the first, including two on third baseman Christian Villanueva's throwing error on Matt Kemp's infield single and Cody Bellinger's RBI single. Seager hit an RBI single in the second.
Perdomo (1-2, 8.36 ERA) is in danger of pitching himself out of the rotation. He was gone after allowing nine runs, seven earned, on 10 hits in three innings. He struck out four and walked two.
He was coming off a five-game suspension for throwing behind Colorado's Nolan Arenado and inciting a brawl on April 11.
''I think I'm always pitching for that,'' Perdomo said of his job. ''Things didn't go well today in the game and all I can do is just go out there and keep working.''
Manager Andy Green said the staff and front office will discuss Perdomo's future. One of San Diego's top pitching prospects, lefty Joey Lucchesi, is already up with the big league club and there's been talk that lefty Eric Lauer could be the next to be promoted.
''We've done a lot to give him every opportunity to be successful at this level,'' Green said of Perdomo. ''He's giving effort. He cares. He does everything he possibly can. He's working hard. It's just not happening. We've got to reevaluate the situation and what's best for us.
''We've been talking about a competitive culture and we intend to give guys opportunities. We have a number of young guys we like in the organization. I'm sure the conversation will be forthcoming here soon as to what's our best move.''
Los Angeles added on in the late innings. Yasmani Grandal hit an RBI double in the eighth while Pederson had a two-run double and Yasiel Puig an RBI single in the ninth.
Pederson, the Dodgers' left fielder, leaped against the wall along the line in an attempt to catch Carlos Asuaje's foul ball in the seventh. He had it in his glove for a split second but it popped out when he came down. Appearing angry, Pederson picked it up and flung it all the way into the third deck. Pederson appeared to be distracted by a fan and umpires reviewed the play for possible fan interference, but ruled there was none.
Dodgers: Placed LHP Rich Hill on the 10-day disabled list with an inflamed middle finger, retroactive to Sunday, and recalled LH reliever Adam Liberatore from Triple-A Oklahoma City.
Dodgers: With Hill going on the DL, the Dodgers are considering whether to move LHP Clayton up a day to oppose Washington RHP Max Scherzer or bring up someone from the minors.
Padres: RHP Tyson Ross (2-1, 3.50) is scheduled to start Friday night in the opener of a three-game series at Arizona.
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