Diagnosing a vacuum leak to fix a hunting idle. I hooked up a smoke machine directly to the airbox side intake where the resonator would attach. I get smoke coming out of three places:

1) A small port directly under the side opening. Looks like it’s some kind of breather hole. Does this need to be plugged or is it supposed to remain open?


2) A small port at the left side of the manifold. This also looks like some kind of breather hole. Should this be plugged?


3) All along the air cleaner cover in front. The attachment points are all broken except maybe two. The center bolt is strong. But it’s been like this for years and I never had a problem, so always assumed this doesn’t matter.


These are all photos I borrowed from online to show the locations, and are not my actual parts.
Thanks.

 

I was wrong about #2. I found a photo from when I pulled the engine that shows a hose attachment going down to that brass thing, which is the PCV (positive crankcase ventilation) valve.


I've reattached the hose. The extreme hunting has gone away and I have an idle of 1100 at cold start (in 23F temperature), however after my engine reaches operating temperature the idle suddenly increases to 2K and drops to 1K once every thirty seconds. I suspect the IACV which I have already cleaned, since I read that for other models the IACV takes control of idle at operating temperature. A new one is $400 so have to do more homework before I'm certain. I also get code P0505.

 

That happened to me, not on my Honda but a Dodge truck I bought. It would idle at about 1500 RPM, turned out to be the PCV valve wasn't seated correctly..