The win gave Phoenix (22-3) the second-longest win streak in league history, passing Houston's 15-game streak in 1998 and moving two games shy of the WNBA mark of 18 straight by Los Angeles in 2001.
Candice Dupree had 16 points and nine rebounds while Brittney Griner added 14 points, seven rebounds and three blocked shots for the Mercury. Taurasi and Griner both sat out the fourth quarter.
The Mercury also won their 11th straight at home, tying a franchise mark set in 1999.
Nneka Ogwumike had 18 points and nine rebounds for the Sparks (12-15), who are now 2-3 since general manager Penny Toler took over as coach during the All-Star break. Los Angeles has lost four of six overall.
The Sparks played for the second consecutive game without leading scorer Candace Parker, who remained in California nursing a left knee strain.
Kristi Tolliver added 14 points and seven assists for the Sparks, who kept it close for more than a half.
Phoenix used a third-quarter run to break open a three-point game at halftime. The Mercury scored 12 straight points, using its break and scoring twice off of steals, to take a 62-45 lead with 3:08 left in the period.
Phoenix led 66-51 going into the fourth quarter and did not allow Los Angeles to get any closer than 11 points.
The Mercury, who lead the league in scoring and hold opponents to the fewest points, were 39.5 percent from the field while allowing Los Angeles to shoot 58 percent although Phoenix still led 42-39 at the break.
Los Angeles scored eight straight points in the first quarter to take a 24-20 lead. The Sparks held the league's best offensive team to 7-for-21 shooting. However, Taurasi and Shay Murphy hit 3-pointers during a 10-0 run that gave Phoenix a 32-27 lead with 6:20 left in the first half.
Phoenix has beaten Los Angeles in its previous three meetings earlier this season.