Chris Johnson homered and drove in two runs as the Houston Astros used a five-run third inning to post a 7-4 road victory over the San Diego Padres on Thursday.

Hunter Pence extended his hitting streak to 14 games for Houston, which has won a season-high four straight. The Astros ended a three-game losing streak in San Diego.

The Padres, meanwhile, continue to struggle at home. San Diego is a National League-worst 9-21 at Petco Park and has scored just 69 runs there.

Houston had no such problems scoring in the cavernous stadium.

Johnson had an RBI single off Tim Stauffer (1-4) in the second and Houston padded its lead in the third with a little help from San Diego, which committed three errors in the frame. Carlos Lee had an RBI double and Brett Wallace drove in a run with a groundout.

Bud Norris (3-4), who added a RBI groundout in the third, carried a 7-2 lead into the seventh before San Diego chased him and scored two runs off reliever Jeff Fulchino. Norris allowed four runs and six hits in six-plus innings.

Wilton Lopez threw a perfect eighth and Mark Melancon worked around a leadoff walk in the ninth for his fifth save in seven chances.