i have a 91 honda accord ex that idles up and down butwhen i take the # 21 vaccume line off it stops. can anyone tell me whats going on with my car

 

When does it do it? When it's cold or running hot at nomral temp?

 

all the time dosent matter on the temp

 

tighten the idle air valvle scew up i had two different ones do the same thing and another one was the intake gasket it sounds the same

 

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.