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Discussion Starter · #1 ·
2004 F-115 Idle 1200 - 1500 rpm after running it for while at 4K rpm there is no code when testing on ears.

Read some forms that the IAC should be cleaned yearly.

Any thoughts in regards to cleaning it?

You think spraying it with silicon lube would help in stopping it from sticking after cleaning it?

F-115, just turned 100 hours today.

Thx.
 

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I would check to be sure the throttle returns to the idle stop first. If the cable is stiff, it may not return all the way. Every so often it is a good idea to decarb the engine. Usually that takes care of the IAC, but if you clean it, try not to use any harsh chemicals.
 

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Your iac valve is an Idle Air Control valve, thus if it is working properley there should be no problem when returing to idle. Also if there was a problem with the iac at idle the values would throw a code to the emm,ecm, whatever you like to call it. Thus setting a code. It is stated in your manualNOT to subject the iac to any solvents what so ever!!!!!!!!!!! Checj that I have no dought. Call me jandemarineandrebuiulds.com
 

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oceansbreeze (4/8/2010)2004 F-115 Idle 1200 - 1500 rpm after running it for while at 4K rpm there is no code when testing on ears.

Read some forms that the IAC should be cleaned yearly.

Any thoughts in regards to cleaning it?

You think spraying it with silicon lube would help in stopping it from sticking after cleaning it?

F-115, just turned 100 hours today.

Thx.
Just read your post again... when you are testing it on the ears, are you running it at 4000 rpm for a while? If so, not good to run the engine at high rpm's with no load for extended times.
 

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J&E Marine (4/8/2010)Your iac valve is an Idle Air Control valve, thus if it is working properley there should be no problem when returing to idle. Also if there was a problem with the iac at idle the values would throw a code to the emm,ecm, whatever you like to call it. Thus setting a code. It is stated in your manualNOT to subject the iac to any solvents what so ever!!!!!!!!!!! Checj that I have no dought. Call me jandemarineandrebuiulds.com
actually the ecm on the F115 does not monitor the IAC, there is no code for it... but there still could be an issue with it.. on these early engines they had an idle undershoot issue that was caused by the ecm.. which was replaced under warranty. I would suspect what David said about a mechanical issue... i would be glad to look at it for you,,,
 

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Discussion Starter · #6 ·
Regarding the RPM -Nevergo more than 2000 RPM and no longer than a 1 minute with ears.

I checked the cables when this first started and again when I had it out last and to me it seem normal,I amcomparing it to howmecurys 2 cycle cables are, I've only own this engine for a year and have not been around yamaha that much, but on the most part they seem very similar to Mercury's.

Whenthe enginedoing this Hi RPM at idle after going few mile @ 4000 RPM, I can put it in neutral, turn off the motor, never touch the controls, restart it and it willreturn to anormal idle90% of the time. Checked for vaccum leaks and haven't found any. And I am not sure regarding the IAC, because whenit does this hi RPM it doesn't always go to normal when I turn it off. But I have notice when it doesn't go to normal 900+RPM then to700 RPMwhen restarting it, and goesto ~1500 RPM it doesdecrease about 300RPM within 30 seconds of starting it to around ~1200 RPM. I figure this is happening due tochanges in pulse to injectors and/or timing advanced being decreased, like under normal starting conditions.

Hopefully today I will be able to check out the IAC and clean it with some Mass Air Flow wire Cleaner and see how it does, which won't be until the next time I take it. While not having any electrical problems, still planning on check battery connections, grounds,cables for higher than normal resistances and/or voltage drops, visibly nothing seem corroded. Checked for vaccum leaks and haven't found any.

Thank you for your time and considerations, will post results.
 

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Question about the IAC. When you turn the ignition key off do you hear the IAC resetting. It will be a clicking noise. Listen carefully fo this, if it does not reset it will give the ECM a false stepper motor count.
 

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You might want to get a computer on it rather than just try fixing things. It could be your throttle plates stuck slightly open also. The others have already told you just about everything you can do for a IAC and throttle cables. If cleaning doesn't do it look for a throttle plate stuck.
 

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Discussion Starter · #10 ·
After a day and half off and on, I figured out and found the problem. I hate intermit problems.:banghead I don't have a laptop anymore,rather buy fishing gear than laptop batteries, so I wasn't able to run the diagnostic on the water where the problem was occuring, and nothing was showing at home when running the diagnostics.

I cleaned the IAC and it seem fine. Recheck linkage again, arrows lined up good everything seem find,but still removed the linkageandrelube them.Check our the electric nodes for higher than normal voltage drops had one with a little higer than normal, and it was on the + battery connection with the wing nut, cleaned connectors and replacewing nutwith a regular nut.

Still acted up on the water, got home and then I got a littlesmarter, got out the heat gunand started to heat different electrical componentand still nothing was running great at home. Iwas whipped, the wife said why don't you try heating that thing upthat near where all the other things you wereheating. Instead of arguing (learn somethingafter almost 40 years of marrage,it not worth it), I figure what the heck, so I appled heat to the lower throttle body had her give it full throttle and then brought it back to netural and then had her started it. Problem show up, 1800 rpms, it drop to about 1500 after a 30 seconds, and within a few minute it went back to normal as the throttle body cooled off.Pulled the pin to the linkage so I could control the throttle at the rear, (I am not that dumb with a prop at my feet) race ita little no problem.Then reheated the throttle body gave it a little gas againand it wouldn'tgo back to normal idle. But once the throttle body cooled after about few minutes while it was running it when back to normal idle by itself.

Removed the intake silencer and was suprised by the corrosion on the back side of thethrottle body as well as some on top by and under the spring which the silencer covered.





Tomorrow I am going to see what caused the corrosion, and disassemble the throttle bodies and clean them up.Hopefully I won't have to put bushing in for the shaft.

As you can see in the picture below after removing the intake, the corrosion is on that one area.



While it not done, at least themystery is over!:clap
 
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