After the first three games of the series were decided by one run each, the Tigers jumped on top early, built a seven-run lead and held on for the win despite being outhit 12-9.
The pivotal fifth game of the series will be played Thursday in Detroit, with the pitchers from Game 1 hooking up in a rematch. Detroit's Anibal Sanchez threw six no-hit innings in the series opener and still barely got the best of Boston's Jon Lester, who surrendered the only run of the contest.
Detroit seized on a stretch of wildness suffered by Boston starter Jake Peavy to score five times on just three hits in the second.
Victor Martinez singled to open the inning, after which Peavy walked both Jhonny Peralta and Alex Avila to load the bases. Omar Infante flew out without bringing home a run, but another walk to Austin Jackson forced home the first run of the inning and a fielder's choice off the bat of Jose Iglesias brought in Peralta.
That brought up Hunter, whose double to left scored Avila and Iglesias. Miguel Cabrera then singled home Hunter. Detroit added two runs in the fourth, a single by Cabrera accounting for one of them.
Doug Fister gave up eight hits over six innings, but struck out seven and allowed a lone run to earn his first win of the playoffs. Peavy surrendered all seven runs on five hits in three-plus innings.