Honda Idle Hunt 2003-2005 Accord 2.4L K24 (Read Description) | DWS

I finally ran into the Honda idle hunting problems, after a lot of diag work, it boiled down to IAC stuck open too much. If your vehicle runs w\o MAF (or is no MAF) you can try this trick to see if IAC or a vacuum leak is the source of the problem. At the end I try to close off the port with my finger slowly but block it off completely and it should make the engine idle way too low or even stall like in the vid to validate there's not a vacuum leak.

Note that the engine in the vid has a MAF which is disconnected (disconnect battery to clear codes) and it will run but has a low rev limit, I touch it in the vid a little.

I'm planning to attempt an IAC delete on this engine and see how that works, there will need to be a slight vacuum leak to simulate the IAC working, if the engine has MAF, the leak should go to the intake tubing.

I've done the same test on my Odyssey van and it had a quick honda idle surge and blocking it off about half way made it idle normally. In the case of this van, it has no coolant so the temp sensor reading isn't right.