In the 1980s and until 1990 he represented West Germany and belonged to the world elite in the decathlon.

His most notable result was winning the bronze medal at the 1984 Summer Olympics in Los Angeles, California.

His personal best result of 8762 points in Filderstadt-Bernhausen on 5 June 1983, placed him third on the world all-time list at that time behind Jürgen Hingsen and Daley Thompson, and still ranks him 14th on the all-time list (as of 2018).

Wentz represented USC Mainz sports club.

During his active sport career he was 1.93 meters tall and weighed 93 kilograms.