PONTIAC, Mich.--Vinnie Johnson scored half of Detroit's points in a decisive 20-8 fourth quarter run as the Pistons beat the Boston Celtics, 113-105, last night to force a seventh game in the NBA Eastern Conference finals.

Game 7 of the series will be played Saturday afternoon in Boston Garden, where the Pistons have lost 17 consecutive games.

The Pistons opened the final quarter with the decisive run to turn an 84-83 advantage into a 104-91 lead with 5:04 remaining.

Johnson and Adrian Dantley led the Pistons with 24 points each, while Isiah Thomas added 21. Larry Bird had 35 points for Boston, while Kevin McHale had 23.

The Celtics, playing without center Robert Parish, who was suspended for slugging Detroit's Bill Laimbeer in Game 5, and without Coach K.C. Jones, who was attending his mother's funeral in California, appeared to tire in the fourth period.

After a basket by Johnson gave Detroit a 108-96 lead, the Pistons' Rick Mahorn grabbed a rebound and threw it the length of the court out of bounds with 3:29 remaining.