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Cleaning the IACV


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#1 Soop

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Posted 12 August 2008 - 01:44 PM

Cleaning the IACV (Idle air control valve.)


What does it do?
The IACV or Idle Air Control Valve, regulates the idle speed by varying the amount of air entering the combustion mixture.
It does this via an electronically controlled solenoid valve, which is activated by the ECU (or Electronic Control Unit.) which determines the necessary AFR (Air Fuel Ratio) needed to maintain a preset idle rpm value.

Why would it need to be cleaned?
It IACV is in direct contact with the inlet tract and and vacuum hoses. And as such comes in contact with all the oil blow by and general grime generated via your engines operation.
This debris can adversely effect the operation of the IACV and in turn cause certain issues.

What kind of issues should you look for?
A faulty or malfunctioning IACV can cause a couple of issues.
Such as irregular idle, such as hunting trough the rpm range and low/high idling.
This in turn can cause the car to stall (in manual instances) of the idle is low or hunting, whilst a high idle can cause excessive fuel usage.

How do you clean it?
Step one:
Locate your IACV.
Depending on what model vehicle you have, the position will vary.
Stricly speaking pre 1999 the IACV can be found in two positions.

Pre 1999 Naturally aspirated Ej20-22-25.

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The IACV has the small beige electrical cap beside the throttle body. You may have to remove the intake pipe work to gain sufficient access to the IACV bolts.

Pre 1999 Single Turbo manifold. (This is an RS Liberty,which is the same as early WRX, so quiet possibly the same layout as the same generation SF Forester.)
If you still have the TMIC or WAIC installed you will have to remove it prior to being able to access the IACV.

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Step two:
Once you have located your IACV and made access possible the removal is quiet straight forward.
You'll need:
* A pair of pliers.
* 1 12mm socket.
* 1 1/4" drive ratchet.
* 1 1/4" drive extension.
* 1 12mm ring spanner.

Once you have these you will be able to remove the IACV.
To do this first you must remove the hoses running to the IACV, don't worry if coolant leaks from the hoses and IACV when you remove them, this is perfectly normal and you wont loose enough to cause you any hassles. You may need to grip the hoses with the pliers and twist them to break the bond between the metal flange and the rubber hose.
Once this is done, you can start on the 12mm bolts. They have a rather fine thread on them so they may take some time to remove, patience is a virtue.

After you have the IACV remove you can proceed to clean it.
At this point i must stress, DO NOT REMOVE THE BEIGE CAP! if you do this, your IACV will be damaged and not function properly.
To clean the IACV i recommend using some Subaru UEC (upper engine cleaner) its availible from all Subaru dealers and is far superior in its ability to remove gum and varnish than most all other carby and throttle body cleaners i have used.
Make sure that you only use the UEC in the mechanical valve component.
For the plug terminal, I use some contact cleaner, which is available at any good electronics store. The reason behind this is because contract cleaner is designed to flash off and not leave an oily residue.

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Once you have done this, and you are satisfied that the valve is clean reverse the removal process to reinstall.
Take care not to cross thread the fine threaded bolts, and not to split the hoses when reattaching them.
Also insure that all Vacuum lines are reinstalled, as if they are not, your vehicle may run rough or not start at all.

I hope this of some value to you, if you have any issues or need some further assistance please feel free to shoot me a PM.

Cheers, Paul.
TSM

#2 Mosti

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Posted 12 August 2008 - 01:52 PM

Nice write up paul Thanks for the link aswell

#3 Soop

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Posted 12 August 2008 - 01:57 PM

No drama's at all mate ;).
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#4 XXB4XX

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Posted 12 August 2008 - 05:05 PM

is it on a brown car? or is the bonnet that badly rusted?

#5 Soop

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Posted 12 August 2008 - 05:15 PM

Quality post. Its a brown VK como bonnet.
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#6 Chaapppppp

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Posted 15 October 2018 - 09:44 AM

Yeah very good explanation dude👍




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