Pence, who grew up in Arlington watching the Rangers play, hit the first pitch of the inning from Jason Jennings (2-2) over the center-field wall. Michael Bourn added a two-out RBI triple to make it 5-3.
After losing five in a row against AL West-leading Texas, the Astros avoided being swept in a season series of at least six games for the first time in franchise history.
Alberto Arias (1-0) struck out the only batter he faced before LaTroy Hawkins pitched the eighth. Jose Valverde worked the ninth for his third save in five chances, the last out coming when Pence made a sliding catch of pinch-hitter Andruw Jones' sinking liner to right.
Michael Young and Chris Davis homered for the Rangers, who wrapped up a 4-5 homestand that trimmed their division lead to 1½ games, the slimmest margin since May 14. The Los Angeles Angels closed the gap with a six-game winning streak.
Houston tied it with two runs in the sixth, when Carlos Lee hit an RBI single before Miguel Tejada scored on a passed ball by Taylor Teagarden. Rangers starter Vicente Padilla was done after that.
Padilla walked two in the sixth and failed to cover first on a ball hit to the right side of the infield that became a single. The right-hander had allowed two earned runs over 12 innings while winning his two previous starts.
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Humberto Quintero was behind the plate for the Astros one night after Ivan Rodriguez broke the major league record with his 2,227th game at catcher. Quintero singled in Erstad with two out in the fifth.
Like Rodriguez did on his record-setting night, Quintero made a run-scoring throwing error on a steal of third. Nelson Cruz scrambled home in the fourth to give Texas a 3-0 lead.
Young homered in the first and Davis connected an inning later against Brandon Backe, who made his first start of the season.
Backe had made four relief appearances since returning May 28 from the disabled list after straining muscles in his left side during spring training. The right-hander started in place of Mike Hampton, who was put on the 15-day disabled list this week with a left groin strain.
Despite allowing three runs in four innings, Backe's ERA dropped from 12.00 to 10.38.
Wesley Wright, recalled from Triple-A Round Rock to take Hampton's roster spot, threw 2 2-3 scoreless innings before Arias struck out Teagarden with a runner on second to end the seventh.
NOTES: The Rangers' last 12 homers have been solo shots, their longest such streak since September 1986. The last homer with runners on base was Ian Kinsler's three-run shot June 5 at Boston. ... Kinsler was 0 for 4, hitting into double plays his last three at-bats. ... Astros manager Cecil Cooper said he was glad to have Rodriguez's record done. But he said Thursday "was a day he was going to get off anyway." ... Lee, usually the Astros' LF, is still hampered by a bad hamstring and was the DH the entire series. ... Houston had won a season-high five consecutive series before losing the first two games to the Rangers.