I have a 1993 accord EX, 5 spd. with the dreaded surging idle - if I drive before the car warms up. The car idles high for about 10 min - 1500 RPM and then settles down to 600.
The other day I followed the honda bulletin re: surging idle diagnosis , posted on this site and here is what I found so far:
1. No vacuum leaks.
2. With IAC valve P2 connector unplugged, there is no suction in lower throttle port, but there is suction in upper throttle port.
3. When I plugged P2 back in, surging started in idle and also another noise - rhythmical hum that seems to originate in same area.

I then took off IAC and cleaned it with carb cleaner, but it didn't look bad. Also, I didn't unhookcoolant lines - b/c I wasn't sure if they are under pressure, will I need to bleed the cooling system afterward? Car has a new radiator 2 years ago and new thermostat 3 months ago.

The FITV seemed to operate normally.

There was mention of checking the Starting air valve?

and how do I check for throttle plate closure? Or can I spray carb cleaner around throttle plate?

It seems like the IAC recreated the symptoms, but I would appreciate any advice or direction. Should I go ahead and replace IAC valve? Can I unhook coolant lines easily or do I risk getting air bubbles in system?
thanks much, wendy

1993 honda accord EX, 4 door, silver, 5 spd, bought this past Jan, because I still regret selling my 1990 accord LX , 5 spd , best car ever, that is still going strong with over 300 k on all original everything!

first car was a 1985 accord DX , hatchback, 5 spd!! and I learned to drive on a 1980 accord sedan LX, 5 spd.

 

Hey man i had the same problem in my 92ex..the cause is one of 2 problems..1.find your fast idle valve,should be on the front right side of your throttle body,it should have 2 phillip screws on the top of it with 2 small coolant hoses going 2 it,remove them,inside should be a plastic ring nut that u can tighten,unloosen it all the way off,under it is a little mini thermostat of some sort,clean the housing,mini thermostat and screw it back in as tight as u can.if that dosent fix it.CHECK your throttlebody adjustment bolt batten it down as much as u can until u hear the idle even out and that should do it..if u still have the problem try replacing the fast idle sensor and that should clear up the problem all 2gether.