Does anyone know the name of this movie?

I seen it on HBO in about 1987. It was an action comedy. It was about 2 cops (1 gay) that go undercover (as a couple) to solve a series of murders in a gay community. I remember that their car was a 196? Volkswagon, thats horn played music. I thought maybe Nick Nolte was in it but I’m not really sure. I’ve googled his movies and it’s not there. So it’s probably someone else. Please help me. I’d like to see it again.