idle up and down...

93 Civic Sedan 1.5 D15b7 Manual...
Ok got the ride where it wilol start up....
the initial start up is fine as it start to idle up a little...but after about 2-5mins the idle starts to go up and down....I can rev it up and it sound fine let off it goes to a reg idle then up and down...

any ideas....all fluids are topped off and all too....