Johnson won a race with Tony Stewart off pit road with 30 laps to go, and from there he kept Stewart behind him for all but one lap to win at Richmond International Raceway.
Johnson now heads into the first of 10 playoff races this week at New Hampshire with three wins in the past seven races -- and a real chance to win his third Sprint Cup Series championship in a row.
"You have to bring your 'A' game every week," Johnson said. "I feel we're there."
The race was scheduled for Saturday night, but NASCAR and speedway officials pushed it back a day to avoid heavy rains from Tropical Storm Hanna.
The delay was tough on eight drivers in the running for the final six qualifying spots for the playoffs, especially on Clint Bowyer. The Richard Childress Racing driver, however, responded with a 12th-place finish to hold on to the final spot in the Chase, eliminating Kasey Kahne and David Ragan from playoff contention.
Johnson's spot was set long before Sunday's race. Stewart, who was trying to get his first victory of the season before starting the Chase, worked beside Johnson several times in the final 30 laps, but Johnson never backed off. Stewart eventually wore out his tires to allow Johnson to pull away in the final five laps for a five car-length victory.
The key, both Johnson and Stewart agreed, was the final pit stop. Stewart came onto pit road with the lead; Johnson beat him back onto the track. Johnson turned track position into another win, while Stewart was left to argue with his race team.
"Track position was everything," Johnson said.
Stewart blasted his team on the two-way radio after the race and sarcastically blaming the loss on a slow pit stop at the end of the race.
Stewart slammed his head and neck restraint collar and his helmet inside the car after the race. He was still upset after climbing from his second-place Toyota.
"We got down there (on the bottom groove) and we couldn't get by," Stewart said. "We couldn't get that run."
Denny Hamlin finished third. Dale Earnhardt Jr. and Mark Martin rounded out the top five.
Reach Don Coble at firstname.lastname@example.org.
1. Kyle Busch 5,080
2. Carl Edwards 5,050
3. Jimmie Johnson 5,040
4. Dale Earnhardt Jr. 5,010
5. Clint Bowyer 5,010
6. Denny Hamlin 5,010
7. Jeff Burton 5,010
8. Tony Stewart 5,000
9. Greg Biffle 5,000
10. Jeff Gordon 5,000
11. Kevin Harvick 5,000
12. Matt Kenseth 5,000
WHAT: Sylvania 300
WHEN: 1 p.m. Sunday
WHERE: New Hampshire Motor Speedway
TV: ABC-Ch. 6
DEFENDING CHAMPION: Clint Bowyer