In 1987 Cotter sold the team to Vince Granatelli (son of former Indy car owner Andy Granatelli) to form Vince Granatelli Racing with Guerrero driving the No. 4 True Value/STP March 87C-Cosworth DFX. Guerrero scored his first Indy car win at the Checker 200 at Phoenix International Raceway. In the race Guerrero originally qualified 3rd, but the car was declared illegal and Guerrero started 22nd (last) to charge his way up through the field to win. At the Indianapolis 500 Guerrero and Granatelli were one of the few teams to have no issues with March 87C as several teams decided to use year-old 86C models instead. In the race Guerrero qualified 5th and was viewed as among the favorites, along with pole sitter Mario Andretti and defending winner Bobby Rahal. In the race Rahal retired after 57 laps due to ignition problems and Guerrero was in 2nd place to Andretti for much of the race. On the 130th lap a wheel came off of Tony Bettenhausen's car and it hit the nose of Guerrero's car and went flying into the grandstand and where it killed spectator Lyle Kurtenbach. On lap 177 Andretti started to have electrical troubles and Guerrero took the lead. On lap 182 Guerrero came in for his final pit stop and as he exited his pit stall the engine stalled. Third gear had been damaged earlier in the race by the Bettenhausen incident and the car began to get moving, only to stop just outside the pit lane. This caused Al Unser, Sr. to take the lead and get a lap on Guerrero. Guerrero finally got going and unlapped himself on lap 191 and there was a caution on lap 192 for Andretti stopping on the track. On lap 196 the restart came out with six cars between Unser and Guerrero. Guerrero was unable to get by Unser and ended up finishing 2nd to one of the year-old March 86Cs to be pressed into race service.