He won the cyclo-cross race the Grand Prix Jean Bausch-Pierre Kellner that year.
The following year he joined a Spanish cycling team Teka with whom he would stay with for the rest of his career.
The following year he became the champion of Germany in the road race and cyclo-cross as well his first stage victory in the Vuelta a España.
Dietzen finished the 1988 Vuelta a España second overall, this time to Sean Kelly of Ireland.
Seventeen years later, the Supreme Court of Spain ordered the organisers of the Vuelta a España to pay damages to Dietzen.