2009 225 vacuum hose question

[Bevhunter]

Ok, so my engine has been idling high for a few weeks and I may have found the culprit. On the rear of the engine, a 2009 Yamaha 225, there is a small triangle box towards the top of the engine that looks like it should have 2 vacuum hoses running to it. There is one hose that runs from the IAC valve to the triangle box, and then there is another hose nipple that is vacant. Can anyone tell me if there is supposed to be a second hose running to that cleaner box and if so, where does it go? It just doesn't make sense for a hose to run to an empty box with a wide open port it unless it contains a type of filter. Any help will be greatly appreciated! Thanks

[fairdeal]

generally, a vacuum sensing hose is small - ~ 1/4" OD
if the hose is much larger - ~1/2" OD - it is 'transporting" air
perhaps into the IAC, or a crankcase breather

outboards typically don't have air filters
but the Yamaha engineers have designed some odd "boxes" associated with air intakes

exactly what rpm is your high idle?
the ECM will "deliberately" increase the idle speed in cases
where it is 'unhappy' with a sensor input
which could be as simple as a disconnected lead

[Bevhunter]

It's one of the larger hoses. When initially cranked, it sits around 1100rpm. I can kill it and crank it right back up and it starts running around 90prpm. If I cover the other hose port on the "box", she purrs around 600rpm. I ran it on yds with no codes, but I know that doesn't necessarily mean all is well.

[Bevhunter]

[fairdeal]

It's one of the larger hoses. ...If I cover the other hose port on the "box", she purrs around 600rpm.

Right.
So that is an air intake to the IAC;
The ECM wants the idle high,
but by choking it off, you get it to idle "normally".

And yes, you don't have a "Diagnostic Record" Code logged

but somewhere in the "Diagnosis" or "Engine Monitor" sections
(which you have to scroll through to see entirely)
there should be an entry which shows what the ECM is unhappy about

[TownsendsFJR1300]

Is it the part next to part #38? :

https://www.boats.net/catalog/yamaha...7/electrical-1

[Bevhunter]

That doesn't look right. The Box is #6 on this schematic: https://www.crowleymarine.com/yp/JX4...txr-2009-225hp

[Bevhunter]

Everything in the engine monitor section was labeled "normal". There may be some values that seem off, but none that stand out to me.

[fairdeal]

well, if the ECM is not telling the IAC to be open,
perhaps it is is stuck in a too-open position -
since you have YDIS -
remove the screws that hold the IAC to the housing
and run the YDIS static test for the IAC:

https://vimeo.com/264625510

the other possibility, I supppose,
is that you have a vacuum leak or not-fully closed throttle plate

which would mean the ECM already has the IAC at 0%
but that still can't keep the idle normal

[Bevhunter]

When running the IAC angle test, the engine drops down to 700rpm and remains there for the duration of the test.

[Bevhunter]

I'll work on it more this evening and try to dial it in.

[fairdeal]

When running the IAC angle test, the engine drops down to 700rpm and remains there for the duration of the test.

hmm.
I've not played with the "active" IAC test.

But seems to me, your result shows the ECM could drop the idle to 700 - if it wanted to.

[Bevhunter]

That's what I was thinking, but it's supposed to step the valve open and slowly increase rpms I believe. Mine holds steady.