I changed the distibutor cap, rotor, and spark plugs and the idle went from 1,000 rpm to 2,500 rpm. what would cause it to do that?

Motor oil, Power Steering oil. Or constant change of weather.

Check that the throttle cable adjustment is correct, and the idle speed adjustiment is good too.

Then check ignition timing.

Check your idle air control motor.It is conected to the plenum(intake manifold).It is conected by 2 10mm bolts. It is not hard to take off. Get a can of carb cleaner and clean the carbon off the tip and spring,as well as spraying it into the passage in the plenum.it's a simple job if you have mechanical ability. usually about 20 min. start to finnish.If that don;t cure it,find a reputable tech. Good luck!

Look again - if it's an 86, it won't have a IAC valve, or a plenum, or a throttle body.

The IAC only exists on fuel injected cars. The carbureted versions do have some functionally equivalent mechanisms, but they are generally vacuum controlled dashpots and things of that nature. The mid 80's carbureted honda engines are devilishly difficult to work on, with a rats nest of a vacuum system. Trust me, I've been in there. If there is a problem with this system, beyond the obvious disconnected or broken hoses, I'd recommend having a professional work on it.

It sounds like the man said the job takes 20 minutes from start to finish. He told you how to do it, with the carborator spray. I've seen my Dad use that before to clean the carborator. He kept it very clean so the engine ran better.