For the 1991 season the team consisted of only six people, and would be the last time a Formula One team entered only one car during the entire season. The car was another version of the C3 from 1989 which had seen some detail work from students of the University of Perugia and which was now called a C4. Enzo Coloni had hoped for Andrea de Cesaris as his first driver, with his sponsorship from Marlboro. The Roman eventually took his experience and his money to Jordan Grand Prix. Coloni handed his single car to newcomer Pedro Chaves from Portugal who had just won the British Formula 3000 series in 1990. The car was out of date, fragile and hard to handle and Chaves was not familiar with most of the tracks. As a result, Chaves never escaped prequalification. Finally he quit the team after the Portuguese Grand Prix. For the following race, Coloni was unable to find a new driver, but for the last two races of the season, he employed Naoki Hattori, a Japanese driver with a very decent record in other formulae but with no experience in Formula One. The results did not improve.