Scott Dixon won the first race of the Houston Grand Prix on a disastrous day for Penske Racing and IndyCar championship leader Helio Castroneves.
Castroneves entered Saturday's race with a 49-point lead over Dixon with three events left on the schedule. But a gearbox issue early in the race led to an 18th-place finish for Castroneves.
Then a slow pit stop by the Penske team for Will Power allowed Dixon to take the lead. The Chip Ganassi Racing driver cruised to his series-best fourth win of the season, cutting his deficit to eight points in the standings.
Dixon swept the Toronto doubleheader in July to climb into the championship race, and he'll try for another sweep Sunday on the course through Reliant Park.
Simona de Silvestro finished a career-best second to earn her first IndyCar podium, and Justin Wilson was third.
IndyCar's first race in Houston since 2007 has had a tough time because of a bump in the first turn that wasn't discovered until Friday when cars hit the track for the first time. Crews used a grinder on the surface all night to try to smooth it down, but it made for disruptions and a rough racing surface.
Then the race itself got off to a tough start as James Hinchcliffe never made it off the starting grid because his car stalled on IndyCar's standing start.
He was lined up in the third row, and cars had to dart around him to avoid a massive collision. Ed Carpenter didn't miss Hinchcliffe, though, and ran into the back of his stalled car. Hinchcliffe walked briskly back to his Andretti Autosport pit stand and tried to compose himself.
"Man, I'm furious. I know what happened, I don't want to talk about what happened," he said. "I'm mad. I'm out of the race. I don't want to get into it here. We've had troubles all weekend with something electrical on the car. We finally got it sorted for qualifying. We were ready, it was go time, and we didn't go.
"We'll regroup. We'll get 'em tomorrow. I'll calm down."
Carpenter had to sit and watch while his team worked furiously to repair his car. His team transporter was in a fire in Arizona while returning from last week's test in California and the backup car suffered smoke damage.
"I was following the cars in front of me, some dust was flying, one of the cars I was following dodged to one side and I tried to dodge to the inside but I clipped Hinch's car," Carpenter said. "It was tough to see with the other cars right in front of me. Just a tough break."
The race immediately went to caution with pole-sitter Takuma Sato out front with team owner A.J. Foyt in attendance for the first time since he underwent hip replacement surgery July 1. But Foyt, serving as the grand marshal for his hometown race, wasn't able to celebrate for long: Sato had to pit on lap seven with a flat tire.
That turned the lead over to Power with Dixon right behind him. The two have had issues in IndyCar's last two races, and it's been magnified because Dixon is racing Power's teammate for the championship.
But the race took a sudden turn when Castroneves headed to pit road on lap 22 with a gearbox problem. The Brazilian sat in his car for an agonizing nine laps as his crew repaired the problem, and by the time he got back on the track, most of his points lead was gone.
It went from bad to worse moments later during green-flag pit stops. Dixon headed in before Power and his Ganassi crew got him out in 7.4 seconds.
Power then made his stop as Dixon was racing around the course, trying desperately to circle the track before Power exited pit road. Dixon did it — in part because the Penske crew needed 9.2 seconds on a troublesome stop for Power.
With Dixon now out front, he had control of the race and the points lead in his sight.