CINCINNATI - The Colts thought they had BenJarvus Green-Ellis down near the goal line.
Instead, the Bengals got a touchdown just before halftime when the call was overturned on review.
The final bad moment in another bad Indianapolis start.
Andrew Luck threw four touchdown passes in the second half, but the Colts were never able to catch up to the Cincinnati Bengals, who kept a safe distance during a 42-28 victory on Sunday at wintery Paul Brown Stadium.
"It wasn't enough," said Luck, who was 29 of 46 for 326 yards without an interception or a sack. "The Bengals beat our butts fair and square, and there's no way to mince those words. The slow start hurt us."
Despite the loss, the Colts (8-5) clinched the AFC South title later Sunday when the Titans lost in Denver 51-28.
"We never like to backdoor your way into the playoffs," defensive end Robert Mathis said. "You want to get momentum, get things on the right track and keep things on the right track."
Indianapolis is in the playoffs but has some major concerns. The Colts were drubbed 40-11 in Arizona two games ago and needed Adam Vinatieri's five field goals to beat Tennessee 22-14 last week.
"We've got some things to clean up, but we certainly came down here with the mindset that we wanted to win this football game and certainly win the division that way," coach Chuck Pagano said.
Andy Dalton regained his passing touch in time to keep the Bengals perfect at home and in control of the AFC North. He threw for three touchdowns and ran for another, making a 21-0 lead stand up.
The Bengals (9-4) kept their firm grip on first place, two games ahead of Baltimore with three to play.
It had been a while since Dalton was this good. He was the AFC's offensive player for October, but hadn't put together a consistent game since.
He was as good as ever on Sunday, helping the Bengals improve to 6-0 at Paul Brown Stadium on a cold, windy day -- 28 degrees at kickoff with a wind chill of 19.
BenJarvus Green-Ellis had a pair of 1-yard touchdown runs -- one of them on a review that overturned a call -- as the Bengals got ahead 21-0 and held on.
The Bengals are having their best season at home since 1988, when they won all eight regular-season home games and two playoff games on the way to a second Super Bowl appearance and loss to San Francisco.
They're in position to clinch their first AFC North title since 2009 with two home games in the last three weeks.
Dalton was sharp from the outset, completing 6 of 7 for 81 yards on the Bengals' first drive, including a 29-yard touchdown pass to Marvin Jones. The Colts have been outscored 49-9 in the first quarters of their past six games.
The Bengals got a pivotal touchdown on a reversed call with 1:06 left in the first half.
They went for it on fourth down from the Colts 1-yard line. Green-Ellis took the handoff and appeared to get tripped by nose tackle Josh Chapman, who dived into the backfield and swiped at his feet.
"I hit his foot when he came through," said Chapman, who started celebrating his play.
Green-Ellis said he felt someone trip him. He stumbled ahead, avoided a couple of defenders, landed at the 1-yard line and slid into the end zone. He was initially ruled down, but the Bengals were awarded a touchdown after a review.
The review focused only on whether a defender touched Green-Ellis as he fell near the goal line, not whether Chapman had tripped him in the backfield, referee Jeff Triplette said.
"We looked at the goal line, (those) were the shots that we looked at," Triplette said.
Trailing 21-0, Luck finally rallied the Colts.
He completed a slant pass that Da'Rick Rogers took 69 yards for a touchdown and another short pass that LaVon Brazill turned into a 19-yard touchdown, slipping through the hands of six defenders.
Dalton and the Bengals never let the Colts get closer than seven points.
Notes: The Bengals moved 2012 Pro Bowl tackle Andrew Whitworth to left guard, and right guard Kevin Zeitler was out of the lineup for the third straight game because of injury. The Colts were missing guards Hugh Thornton and Jeff Linkenbach. ... Colts RB Chris Rainey will get an MRI on an injured ankle. ... The Bengals have scored 49, 41 and 42 points in their past three home games, the first time they've scored at least 40 in three straight at home. ... RB Giovani Bernard had 99 yards on 12 carries, coming up a yard short of the first 100-yard rushing game by a Bengal this season. He also had 49 yards on four catches.