trying to install a tach in a 91 civic 5 spd,what color is the wire for the tach sensor and where would it be?

Answer 1

Those after-market tachs used to work by sensing the voltage surge on the coil. A Honda probably doesn't have the coil, too modern. If you found a tach at a recycle place, you'll have to find a similar model Civic and trace down the wire.