Cold idle speed high

[AmTeC]

So I've been told that in hondas like my cb7, the idle speed is controlled by coolant flow. When I bought my CB7 in november, The idle would surge up and down whenever it was in park or neutral, and most of the time when it wasnt surging it would be idling around 1100-1200 rpm. It also had a thermostat which was stuck open, I changed that and decided to flush the coolant while im at it. I put in coolant and bled the system of air and it was fine ever since, idle went down to 850 rpm when warm, no more surging. Recently I found a pretty big hole in the expansion overflow hose right where it connects to the radiator neck, it was leaking coolant (engine was hot when I discovered this) I'm not sure how much leaked out, wasnt very obvious. I just snipped off the damaged section of the hose and reconnected it, no big deal. Today I noticed that when I start it up from a cold start the rpm shoots up to like 2500 and doesnt go down until the engine is starting to warm up, once warm, the idle is at 850 like normal. I haven't gotten a chance to check the coolant level because my dad drives my cb7 all the time because he likes it more than his own car -_-

But could low coolant be causing the high idle?

[Fleetw00d]

The normal idle speed is controlled by the Idle Air Control Valve (IACV). It is located on the center front of the intake plenum. There is a stepper motor in the valve that controls additional air above and beyond what is coming through the Idle Screw in the throttle body. Normal hot idle should be 700-750 rpm.

There is a Fast Idle Thermal Valve (FITV) that operates on coolant temperature. This valve is located on the front left of the intake plenum. Coolant is routed through the IACV and over to the bottom of the FITV. There is a thermal actuator in the coolant section of the valve that controls the preload on a spring loaded plunger. With cold coolant, the preload is low and allows engine vacuum to pull the plunger down allowing for air into the plenum for a fast idle to help the engine warm up. This should be approximately 1700 rpm after first starting a cold (say 32 F) engine. As the coolant warms up, the thermal actuator increases the preload on the spring and slowly closes off the extra air so that the IACV controls the idle.

Insufficient coolant can result in coolant not being circulated to the FITV so that the engine speed may remain higher than it should. This could also be caused by a vacuum leak anywhere in the intake system downstream of the throttle body. Top off the coolant and bleed it again. I also suggest that you replace the o-ring on the light yellow piston in the FITV as described here: http://www.cb7tuner.com/vbb/showthread.php?t=206012

[7beast]

Fleetwood pretty much covered it all.. make sure u also "burp" the cooling system good

[zedjr10]

low coolant or leaking coolant would cause it to surge more than just stay at one idle imo. That might be ur iacv needs to be cleaned possibly with ur fitv turned down a little. I was playing around with mine before and after i cleaned the iacv and if i turned up the fitv too high before i cleaned the iacv it would idle really high(2500rpm) and after a minute or so i would get a loopy idle. I cleaned my iacv first with carb cleaner and then tightened my fitv all the way down and then started my adjustments and all is perfectomento. Don't adjust ur idle screw on the iacv as am told that is set at the factory according to piston position or something(i really have no ideal) and is set for life of car.

[GhostAccord]

^^^This also goes for the idle set screw and throttle stop. No need to adjust ether of those. the IAC and FITV will make all air bypass adjustments both electronically and mechanically.

Do not touch the set screws on the IAC or throttle body!