SONOMA, Calif. — Marcos Ambrose had his first career Sprint Cup Series victory in sight when a late caution threw a roadblock into his path.

SONOMA, Calif. — Marcos Ambrose had his first career Sprint Cup Series victory in sight when a late caution threw a roadblock into his path.

Then his own bizarre gaffe cost him the win.

Ambrose stalled his engine while trying to conserve gas late in Sunday's race at Infineon Raceway, where his car came to a stop while leading with six laps remaining. He restarted and tried to re-claim his position at the front of the field, but NASCAR ordered him back to seventh place and Jimmie Johnson inherited the lead.

Johnson then cruised to his first career road course win, while Ambrose had to settle for a disappointing sixth-place finish.

"My bad," the Australian said. "I'm disappointed. It's NASCAR's house and I'll always play by the rules. I don't agree with it, I don't like it and that's only because I lost the race because of it.

"I had the motor turned off trying to save a bit of fuel and just had trouble getting it fired again. That's it."

It was yet another cruel defeat for Ambrose, a road racing ace who has fallen short of victory several times in NASCAR because of various reasons.

He was spun by Robby Gordon while leading the Nationwide Series race at Montreal in 2007, and last year was passed by Carl Edwards in the final turn at the same track. Although he has two career Nationwide wins on the road course at Watkins Glen, he's winless in the Cup Series despite three top-three finishes in five career road course races.

"I feel bad for him," Johnson said. "It was definitely a gift kind of handed to us."

The four-time defending series champion won for the fourth time this season, but first since Bristol in March — a 10-race drought that had many wondering why Johnson was "slumping."

Aside from ending the slump, Johnson more importantly added a road course victory to his resume and knocked Sonoma off the list of five active Cup tracks where he had never been to Victory Lane.

But road course racing has never been his strength in NASCAR. He went into Sunday's race with an average finish of 17th at Sonoma, which caused him to enter two Grand-Am races this season in an attempt to gain extra practice at making right and left turns.