F115 IAC valve

[Flflyer19]

My 2004 f114 all of a sudden would not idle. It has stopped making the rattle noise from the IAC valve at shutdown. When turning the key on I can feel the valve make a slight click but thats it. I read that this can damage the ecm . My question is if the IAC is unplugged and the motor is run can the ecm still be damaged? Also does this sound like a typical IAC failure? Have not run any diagnostics.

[boscoe99]

The IAC valve upon becoming defective has been known to damage an ECU.

If disconnected I don't see it damaging the ECU but then your motor may not idle correctly (if at all). The ECU will sense the IAC valve is disconnected and may not allow the motor to run at higher RPM.

Perhaps the valve has become stuck. Have you tried cleaning it to see if the situation improves?

Best situation would be for a mechanic to connect the motor to a laptop computer running Yamaha software in which case the IAC valve can be told to open or close. If it is told what to do but doesn't want to do it then either time for a cleaning or a replacement valve.

[Flflyer19]

I didnt think it would since there wouldnt be any voltage when the ecm grounds to move the valve. I have ordered the ysd software but wanted to use the boat. I cut into the top of the IAC and turned the motor manualy to get a good idle . I dont think the ecm gets any feedback from the IAC but anyway it runs well like this . I will be looking for a IAC valve to replace the one but until then didnt see how it would hurt the ecm being unpluged. Just want to be sure. Thanks

[boscoe99]

I didnt think it would since there wouldnt be any voltage when the ecm grounds to move the valve. I have ordered the ysd software but wanted to use the boat. I cut into the top of the IAC and turned the motor manualy to get a good idle . I dont think the ecm gets any feedback from the IAC but anyway it runs well like this . I will be looking for a IAC valve to replace the one but until then didnt see how it would hurt the ecm being unpluged. Just want to be sure. Thanks

Excellent. I like a fellow that experiments.

[rodbolt17]

the ECM has no method of actually detecting if the ISC is plugged in or tossed in the creek.

it will attempt to move the valve anyway by applying the ground path.
but with the valve unplugged there is a bit of an open circuit.
with the ISC fixed the ECM can no longer control the engine idle speed and you may see some intake air codes.
its going to see all the other sensors responses yet the idle speed not changing so it may make assumptions.

[Flflyer19]

Seems to run fine do you think I will do any damage running like this until I find a valve. I may have to take a chance on a used one. $380 new is insane , ,Yamaha must think they are in the drug buisness.

[boscoe99]

It is only .38 of one boat unit.

You got eleven years service out of yours. Don't know your hours but think of how many cycles the valve might have made over its life. Yamaha does not offer cleaning of the valve but maybe a few cleaning years ago might have extended its life.

Be glad that your failed one did not damage the 1 boat unit ECU.

How easy or difficult is it for you to manipulate the valve to get the motor to idle where you want it? Do you idle a lot or do you run at power most of the time?

[boscoe99]

Seems to run fine do you think I will do any damage running like this until I find a valve. I may have to take a chance on a used one. $380 new is insane , ,Yamaha must think they are in the drug buisness.

Now that I think about it, a crafty fellow such as yourself might be able to take your existing IAV valve to a good autoparts store and see if they have one that is identical, or all but identical, to the one that you have. The F115 is based on a design by Ford Motor Company (internal parts are branded Ford) so it is very likely that an IAC for a Ford, say a 1.8 liter Escort, might very well use the IAC that your Yamaha does.

For instance

Mercury Marauder Idle Air Control Valves

[rodbolt17]

the ISC does several functions, it aids in con*****ing idle speed at start up and warm up.
without it you may suffer cold engine stalls and may have to use the throttle similar to an old two stroke .

it also goes to 100% above about 1300 RPM and remains there until the engine speed is decreased by throttle down.
it now acts as a dashpot.
without it you may experience stall at throttle down.

[Flflyer19]

So far no stalling problems , Idle is adjusted turning the motor from a hole in top and it is stable.I guess it may change with conditions but so far very stable. Do you think I can do any damage running this way ? Hate to sound cheap but 380 is over the top for this part. Would like to look around and find one but would still like to run the boat for now.

[rodbolt17]

wont hurt anything but be aware of potential stalling issues.
there is NO idle speed adjustments on that motor.
you set everything up CORRECTLY and the ISC does the rest.

don't start randomly monkeying with a screw just cause you have a driver.

[NW Drifter]

Guys, I have the idle problem out of the blue on start up this season. It pulses at idle on my F150 and doesn't make the rattle sound on shut off. BUT I cant find the ISC.... Where is it hiding?

[pstephens46]

Guys, I have the idle problem out of the blue on start up this season. It pulses at idle on my F150 and doesn't make the rattle sound on shut off. BUT I cant find the ISC.... Where is it hiding?

Item 26 on my 2005 example below. Start a new thread for your motor and include exact model. Edit: pic is pretty bad, posted from phone. Maybe it is a bit sharper viewing from a desktop computer.

[pstephens46]

Above pic looks worse on desktop.....Here is a link. #26

https://www.boats.net/catalog/yamaha...0txrd/intake-2

[TownsendsFJR1300]

Above pic looks worse on desktop.....Here is a link. #26

https://www.boats.net/catalog/yamaha...0txrd/intake-2