The Pistons, whose collective heart was questioned by one of their players, played hard for three-plus quarters before being rendered helpless by James.
He had an alley-oop slam midway through the fourth quarter during an 18-2 run that started after the sixth tie of the game.
James had help, getting a career playoff-high 19 points and 10 rebounds from Joe Smith, and 13 points from Zydrunas Ilgauskas.
The Pistons will host Game 4 on Sunday, needing a surprising showing to extend the series.
Detroit coach Michael Curry said the Pistons needed both Rasheed Wallace and Tayshaun Prince to play well to have a chance to win, and neither did.
Wallace scored just five points, looking old, banged up and disinterested. Prince scored seven points in the first quarter and was held scoreless the rest of the game, laboring with a sore back.
Detroit's Richard Hamilton had 15 points, eight rebounds and six assists, while Rodney Stuckey contributed 12 points and five assists.
Antonio McDyess, who had eight points and eight rebounds, lamented the fact that his team went through the motions when it lost the first two games of the series on the road by an average of 15 points.
The Pistons played with pride early, scoring the first eight points and refusing to go away when they fell behind by nine in the first half.
Detroit took turns with the lead in an ugly third quarter - scoring 16 points and giving up nine
- but had no answer when James chose to take over the game in the fourth quarter, scoring 11 points.
His final points in the first half came on a sequence that made the Cavs laugh and the Pistons pout.
