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enigmas
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Discussion Starter #1
Hi guys, I'm heading towards the completion of the rebuild of my burned VROD and am now up to sorting out some of the minor issues of components that were effected by the heat of the fire...such as the IAC.

I've posted some text across (see below) from the Technical Section as the nature of the problem has changed.

Idle Air Control Motor.

I started the engine tonight and wedged some cotton cloth in the well between the butterflys of the throttle body where the bleed port for IACM is situated. By restricting the flow of air in this manner I was about to get a really nice idle speed and the engine would still rev cleanly.

Given this I'd say the IACM is cactus!
The large pintle that controls air flow at idle seems to be fully retracted allowing the port to draw a maximum amount of air.

There are 4 pins on the IACM... how do I check it for operation on the bench? The ECM has 4 pins all designated IACM...this doesn't tell me much?

*I have an old 6 volt motorcycle battery that registers less than 6volts that I could use as a power source.


Bob's Response

In the manual on the IAC, it states there should be a "park" procedure every time the key is turned off after being on more than 2 seconds. The pintle should first fully extend, then fully retract to prepare for the next start, it takes 10 seconds to cycle. Try this once and see what happens. I can't find a voltage correlation to test the IAC on a bench, it shows the wires, 2 "high" and 2 "low". I was half expecting the bike to die when you blocked the airflow if the IAC was the problem, I'm wondering if there's a vacuum leak-maybe a rubber part melted.

My response

Bob, I'm at work so I'm rushing this response. I tried a ground and 4.5 volts on all pins of the IAC motor and nothing happens. I reckon the IAC is 'stuffed' to use an Aussie term. The pintle is fully retracted and so a maximum amount of air is entering the idle port. (I could always cobble up a (mechanical) needle valve adjustment if I'm desperate...although the computer would definitely be out of the loop. Even restricting it in the way I did, its possible to get a really nice even idle)

Guys please chime in here if you have any specific knowledge about testing the function of the IAC motor
 

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enigmas
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Discussion Starter #4
Thanks guys, Nothing seems to happen. I'm starting it with the complete air-box and filter off so I have good access to the throttle body.

If I put my hand on it and switch the key on and off I can't feel anything. I'll remove it from the throttle body but leave the plug connected to visually check.

I've just done the above test and I can feel something as I turn it on and off.

Oops...just made the mistake of cycling it too much and the pintle shot out (as stated in the text of the above link)

Will now attempt to put it back together!

If I put the pintle back into the motor I can turn it approximately 3 times with my thumb and forefinger...then it stops.
Is there a correct seated position?
The pintle seems to be further extended than when it was apparently jambed and non operational.

Take 2
I put the IAC motor back into the throttle body and can now see the pintle extend through it's tapered seat viewed from above.

* When I turn the ignition on now it fails to retract? Any ideas?

* Is there a preset distance for the Pintle to Extend before the IAC motor is fitted the the throttle body?

Note: Been doing a bit of research the IAC motor is a GM product
 

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I'm thinking there's some rust inside the IAC from the fire hoses, not sure if you sprayed any penetrating oil into the IAC while the pintle was retracted. Sporadic functioning sounds like some future headaches while riding, high idle=hard shifting, no idle=dieing when you stop. The pintle should retract when you turn the key off.
 

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enigmas
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Discussion Starter #6
You may be right Bob. I cycled the pintle out again and squirted some penetrene down the shaft hole and then reassembled it again. If you're doing this you need to connect it to the plug (while its out...holding it in your hand).

If you look at the diagram and the measurement is 25mm its fully extended and will cut all air to the idle port. If you hold the unit while pressing firmly on the pintle end (ignition on) press the run switch on and off several times pausing between each time and the pintle should retract. Fully retracted is 20mm. Once the pintle is retracted fit the IAC back to the throttle body. Turn the ignition on again and work the run switch on and off (pause a bit when you do this as the pintle reacts quite slowly)

When the IAC is in it's housing you can view it from above the throttle body and you will see the pintle end cycle back and forth slowly. From it's retracted position when activated it moves forward against its tapered port till it can no longer move and then counts backwards...moves back a bit.

Suffice to say...it's now working on my scoot and the idle is where it should be.

You can check resistance on the pins by setting a multimeter to ohms (2K). Of the 4 terminals probe the outside 2 then the inside 2 in turn. They both should read about 50 - 55 ohms. Apparently if these pins read about 10 ohms its cactus.



Once again thanks for the assistance guys. Hopefully this info will be of assistance to someone else.
 

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IAC allways working

Hi, guys
yesterday after a long run, switched the engine off, i could hear the iac working. When i turn the key to "on", i don't hear it any more. Te bike runs, the problem is that i have to remove the 15a fuse every time i stop...
i have to notice that i baugth a black rear ligth last week, and it's bulb went really too hot .
Any idea about the problem? thanks
Michel
 

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Hi, guys
yesterday after a long run, switched the engine off, i could hear the iac working. When i turn the key to "on", i don't hear it any more. Te bike runs, the problem is that i have to remove the 15a fuse every time i stop...
i have to notice that i baugth a black rear ligth last week, and it's bulb went really too hot .
Any idea about the problem? thanks
Michel
:vrodforu: Michel, the IAC is supposed to cycle when you turn the key off, it's preparing for the next start cycle. It goes from fully closed to fully open then back to start opening, around 30 seconds after you turn the key off is nothing to worry about.
 

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IAC allways working

Hi, and thanks for this prompt answer, unfortunately, the iac never stops, even 3 hours after turning off the key... i will open the airbox again, i don't know if it is due to the iac itself or an other electrical cause!
 
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