During the development and testing of the new M291 powerplant, it became apparent to Sauber Mercedes that there were problems in the engine design and construction. Thus the team started the 1991 season with a lone C291, while at the same time running an older C11. In the first two races of the season, the C291 failed to finish while the C11 finished 2nd and 3rd. At the third race, the C291 scored a 2nd-place finish, ahead of the C11. For the fourth round, the 1991 24 Hours of Le Mans, the team decided that the C291 would not be capable of completing the race, and thus were forced to enter three C11s.