Re: hay 91 accord idles up and down
apparently, idle surging happens with any vacuum leak.
i once had to unbolt my egr valve and had to leave it on loose; i started and ran the car - it was surging.
it just so happens that the fast idle thermal valve tends to be the most common (naturally occurring, when cold) source of a leak on hondas, though that may not be the case here.
try to find out what the source of your vacuum leak is -what is vacumm line 21 hooked up to?- and fix it.