BOSTON — Ray Allen raised his arms to fire up the Boston crowd with 4.5 seconds left.

The struggling Celtics sharpshooter already had excited the fans by finding his shooting touch Wednesday night and helping Boston move one win away from its first NBA finals in 21 years.

"My feeling now is no different from if I had scored 10 points and we still won the game," said Allen, who scored 29 in the 106-102 win over the Pistons. "It's a great feeling because (of) the joy on everybody's face."

The Celtics lead the best-of-seven Eastern Conference final 3-2 and can wrap it up Friday night at Detroit. If not, Game 7 will be in Boston Sunday night.

But their joy nearly turned to misery as they let a 17-point lead with 1:19 left in the third quarter drop to 100-99 with 1:23 to go in the game.

Then Boston took a 20-second timeout to set up a play for Allen or Kevin Garnett. Allen caught the inbounds pass from James Posey and immediately took a shot from the left corner. It went in and the crowd roared.

"I assumed he threw it because I was open," Allen said. "Posey made a play and it was time for me to put the shot up."

Rodney Stuckey hit two free throws to make it 102-101 with 8.2 seconds left, and Allen followed with two more to restore the 3-point lead with 6.3 seconds remaining.

Then Stuckey was fouled and, as Allen played cheerleader a few feet behind him, the Pistons rookie missed the first shot then made the second. Garnett, who led all scorers with 33 points, finished with two free throws with 3.4 seconds to play.

"We knew the significance of this game," Garnett said. "You don't win this game, you put basically yourself in a corner."

Now the Pistons, in their sixth straight conference final, must win at home to have a chance at their second NBA title in that span.

"Our experience and our being in this for so long and being in so many tough situations, and us being at home helps," said Chauncey Billups, who led Detroit with 26 points. "Those are the kind of things that you've got to lean on."