Billingsley (8-7) gave up six hits, struck out five and did not allow an earned run to win his fourth straight start. The Astros scored in the fifth on J.R. Towles' two-out, two-run double that followed Luis Maza's error at second base. Maza replaced Jeff Kent, who left in the fifth inning with a stiff back.
The 23-year-old Billingsley said the pitch to Towles was his only mistake. He said he threw only three offspeed pitches through the first four innings and didn't start throwing breaking balls until the fifth.
"I was getting the fastball in for strikes on the first pitch and I was able to get ahead in the count," Billingsley said. "I was just sticking with the fastball."
Los Angeles has been stricken with injuries throughout the first half of the season but has kept pace with Arizona in the NL West. Help is finally on the way -- Nomar Garciaparra and Andruw Jones are due to come off the disabled list and join the team on Friday when the Dodgers open a three-game series in San Francisco.
The Dodgers won three in a row in Houston without the All-Star duo, another encouraging sign for manager Joe Torre.
"We played these last three games with just a sense of determination," Torre said. "I just have a good feel just about how we've gotten after it."
Los Angeles scored all its runs off Brandon Backe (5-9) and took the lead in the first inning for the fourth straight game.
With two outs, Russell Martin singled and Kent walked before Loney dropped a blooper just inside the left-field line. The ball bounced into the stands for a ground-rule double, scoring Martin but forcing Kent to stop at third.
DeWitt followed with a two-run single to right-center. The rookie third baseman was 3-for-25 in his previous 10 games.
Backe said Loney's double was the biggest hit of the game.
"That was the back-breaker more than anything," Backe said. "It was a well-placed ball and it was just kind of the way the day started. If that ball goes foul and I get him out, there's no telling what would've happened."
Ethier led off the third inning with a solo homer to left, his ninth of the season. He also hit a solo shot in Wednesday's 4-1 victory.
"He was as good as he could be," Torre said of Billingsley.
Kent lined out to end the Dodgers' fifth and left the game before the Houston half of the inning. Maza, who started the game at shortstop, moved to Kent's spot and Angel Berroa came into the game to take Maza's position.
Torre said Kent's injury wasn't serious and that he hoped to play the opener in San Francisco on Friday.
With two outs, Maza mishandled Geoff Blum's grounder and Hunter Pence followed with a single to right. Towles then doubled off the left-field scoreboard to make it 4-2. Towles was called up from the minors on Tuesday night after regular catcher Humberto Quintero suffered a concussion when he was hit in the head with a bat.
Towles' hit was about the only blemish on Billingsley's outing.
"We make that play at second base and he may not give up anything," Torre said.
Loney led off the sixth with a solo homer to left, his seventh.
Carlos Lee doubled in the sixth, but Billingsley retired the other three hitters he faced. Billingsley threw only 66 pitches in the first six innings. He still looked strong in the seventh, striking out Pence and Towles to end the inning.
"None of his pitches were the same," Pence said. "They were moving all over the place."
Loretta singled with two outs in the eighth, but Billingsley struck out Berkman looking. The Astros' slugger, leading all NL first baseman in All-Star ballots, went 1-for-12 in the series.
Houston manager Cecil Cooper said right-hander Roy Oswalt will miss his next scheduled start, Saturday in Atlanta. Oswalt strained his left hip in Tuesday's 4-1 win. Cooper said reliever Chris Sampson start in Oswalt's place and Oswalt would return to the rotation some time next week. ... The Dodgers announced after the game that shortstop Rafael Furcal had no complications in his back surgery Thursday. The procedure was performed by Dr. Robert Watkins at Marina Del Rey Hospital in Los Angeles. Furcal, on the disabled list since May 6 with lower back pain, will stay in the hospital overnight and be discharged on Friday. Torre said Wednesday that Furcal is expected to miss at least eight weeks.