Gentlemen, and any ladies who might be present... I have an issue that I hope someone can help me with. I'm fairly new to the forums, and to Hondas in general, but my limited time here has helped me greatly thus far.

I have a rolling idle problem. When cold it idles at around 2K then drops down to surge between 1500 up to 2200 rpms.

Thus far I've removed/cleaned both the IAC and the FITV to no avail. I did every proceedure outlined here to both when removing and cleaning. I was informed by a Honda Tech that when rebuilding the FITV after cleaning to screw it down to the bottom and then back off a turn and a half.

I then investigated the base idle reset thinking maybe I needed to do that and clear the ecu to get the idle to where it needed to be. When warmed up and the IAC plug removed, it idles @ around 1K and jumps up to about 1300 rpm. I located what I believe to be the throttle screw (recessed in a small hole above the throttle bore) and it was tightened all the way down, I loosened it (by unscrewing the other direction) but never got the idle to change.

Any chance I was turning the wrong screw, or is there something else wrong. I've looked for vaccuum leaks and come up empty. But with as little as I know about these cars it's possible I'm overlooking something.

This idle issue is really frustrating, please help me before I shoot this damn thing.

 

There are 3 valves that allow air to bypass the throttle body and can mess up the idle. The FITV (#8), IAC(#15), and the air boost valve (#9). See pic below.

What you want to do is remove the intake hose from the throttle body. Start the car. There are two ports inside of the throttle body that allow air to bypass the throttle plate.

When the engine is cold, both ports should pull a vacuum. The lower one is controlled by the FITV. The upper is IAC controlled. Plug the lower FITV port with your finger. The idle should stabilize if it is a FITV problem. Plugging both ports should cause the engine to stall.

Once the engine warms up, you should feel very little vacuum on the FITV port when covering with your finger.

You should be able to plug the air boost valve by blocking off its port in the intake tube where #22 plugs into the intake tube. Alternatively, you can pull the vacuum hose from the intake tube and plug the end of #22. If this stabilizes your idle, then that valve is the likely problem.

 

Thank you for your response and the helpful diagram. So should the idle not stabilize, then I'm guessing it's time for a new FITV.

Also should it turn out to be the air boost valve, and I delete it completely, would it hurt anything? I'm of the thought that since I live down south it shouldn't hurt since it appears to be primarily used to help warm up a cold engine during cold temperature starts.


::EDITED::

Pulled the vac. hose from #22, plugged it w/my finger, and no difference. Can you show me on the diagram where the ports are located on the throttle body?

Once again I appreciate the help.

 

Its the opposite. If the idle does stabilize, then you have identified the culprit. You are blocking the valve with your finger to take that component out of the idle control.

I think the FITV is the valve that allows extra air to enter the engine when it is cold. I am not exactly sure when the air boost valve comes into play. If this were my car, I would pick up the air boost valve from a junkyard and replace if it turns out to be the culprit.

You can also spray throttle body cleaner around those three valve to see if a bad gasket is allowing air to enter the intake. The idle would drastically change if you spray onto the leaking part. You want to be careful, because that stuff is flammable. It is always a good idea to have a fire extinguisher nearby when you do this kind of stuff.

 

Ahhhh I understood backwards. Thanks for straightening me out on that. I've sprayed carb/t.b. cleaner around the intake looking for a leak, as well as around the hosiery looking for same. I've not found any yet, but I'll hit it again to see if that might be the culprit.

 

Just for grins.....have you pinched off the PCV hose to see if the surge stops? If stuck open it can cause a surge,,,DOES not explain the high idle.

 

I have discovered the ports listed above, and apon plugging the lower (both are on the left side of the throttle bore) port the idle has no change. However when I plug the upper port Only the car will stall and die. Does this mean that my IAC is bad?

::EDIT::

After futher contemplation, I'm thinking that if the upper port is IAC, my plugging it completely caused it to stall and die because the IAC wasn't getting any air at all. I went back out re-started the car and Partially covered the port and it purred like a kitten, once I'd found the proper finger adjustment.

Possible conclusion: Maybe the IAC needs some adjustment. Is that possible?

 

You verified that the FITV is ok (lower port plugged, no change). The IAC may or may not be the problem.

Did you plug the hose at #22?

 

yeah I plugged #22. no change noticed in idle. I'm really stumped. I've looked EVERYWHERE for a vac leak, and come up empty. Any other suggestions guys?

 

bump