PLEASE READ THE THREAD "a really bad idle"

i found a honda technical service bulletin and wrote it word for word in the thread. i can't guarantee this will fix things but i hope it helps someone.

why don't you post it here?

man i thought i posted the bulletin on really bad idle. sorry. well here it is. first off, the 2000 rpm idle at start up is good. that is the fast idle to help warm up the engine. there is nothing wrong with that. now about the surging idle after the fast idle kicks off. the honda technical service buletin states that it could be the fast idle control valve. check your base idle and vacuum leaks. if good check the fast idle control valve by lifting up the black cover(on the belt side of an 86 si hatch) and listening for vacuum on the control valve while it is surging. if you hear it then it is bad. there should be no vacuum there since you want normal idle, not fast idle. if you can't hear it pinch off the vacuum lines to the valve WHILE IT IS SURGING( or hunting for idle, whichever you want to call it). if the idle goes to normal there is your problem. replace the fast idle control valve. i didn't hear it so i pinched the lines and the surging quit, that's how i found it on my car. hope this helps.

oh yeah that is what honda says. i haven't fixed mine yet so i can't guarantee it but i'd listen to honda. that's why i am going to replace it and find out.

p.s. you have to disconnect the hoses from the control valve and listen for vacuum. don't try to hear it with everything hooked up.

if you replace the O2 sensor with the universal bosche 1-wire and do not sodder it correctly, it will cause idle problems. it might not show up right away. (just another thing to check if the above didn't give satisfaction)