For some reason my 1997 civic ex d16y8 keeps going from 1000-2000 rpm will idle even if it’s cold or warm. But while driving on the freeway I don’t notice anything only when I’m idle

 

Unmetered air is getting past the throttle plate. This could be a vacuum leak, a bad IACV, bent throttle plate, etc. Start by making sure all vacuum lines are connected and inspecting the lines for cracks or breaks.