Idioms in Speech
(1) to do smb a favour,
to do smb a good turn
them too and that you're just dying to do them a favour. It's sort of funny, in a way. (J. Salinger)
2. This is for a friend who's done me a good turn. (1. Mur¬doch)
3. "1 came to do you a good turn," she said. (J. Wain)