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Author Topic: How To Clean Your 2.0L IACV and Breather Jet  (Read 19508 times)

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Grumpy

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How To Clean Your 2.0L IACV and Breather Jet
« on: 02 November 2007, 12:44:13 »

We seem to keep getting the same question on the 2.0L 16V
stalling. Mine and others answers seem to be spread over
numerous threads, so I've dragged it all together here.

Although there are several reasons why it will stall, one of the
most common is the Small Breather  Jet blocking up, and causing
the Idle Air Control Valve to malfunction. So this 'How To' will
just deal with checking for, and rectifying, this condition.

I don't believe in 'Monkey See, Monkey Do', so I'll try and explain
how the system works, at Idle. You must understand how something
works to be able to work out what will cause it to fail.
So below is rough, hand drawn schematic. It's not to scale and
it doesn't show everything. So pedants will have a field day,
but it should illustrate what you need to know.
Have a look, and then read the explanation below it.
I've followed it with a picture of the real engine bay.





As you can see, the Air flows in through the filter and into the
top of the Throttle Body to the Top of the Butterfly Valve, shown
in Red. Because the Butterfly is closed at Idle, the Air flow to the
Engine passes through the Idle Air Control Valve (IACV). Just follow
the Blue Arrows to see the flow. Note that the Inlet to the IACV is
above the Butterfly Valve and the Outlet is below it. This means that
the Air Pressure is Higher on the Inlet and above the Butterfly, than
the Outlet and below the Butterfly. This is due to the 'Suction' created
by the engine which is blocked off by the closed Butterfly.

Also note that the IACV is a Twin Valve arrangement, with the Air
passing round the back of the IACV to give flow through the Second
Valve as well as the first. This is important to understand for when
you clean the IACV. But more on that later.

Now note the 2 Breather hoses coming out of your Cam Cover.
The larger hose connects to the Intake Trunking between the
Air Filter and the top side of the Butterfly, so is subject to the
relatively Higher Pressure than the relatively Lower Pressure
underneath the Butterfly.

The Smaller Breather Hose is connected to a Jet that connects
below the Butterfly Valve, so is subject to the relatively Lower
Pressure.

So this means that the Smaller Breather Hose is connected
to a Lower Air Pressure than the Larger Breather Hose.
So, during normal Idle operation, the oily fumes will travel
towards the Lower pressure, via the Smaller Breather Hose,
and will not pass through the Throttle Body and IACV.

Now then, what goes wrong?
The smaller breather hose connects to a JET that narrows
down to approx 1.6mm. If you remember your Gas Laws,
Pressure1 divided by Temperature1 = Pressure2 divided by Temperature2.
So, as the Air whistles through the 1.6mm jet, it suffers a large
pressure drop. This means that it must also suffer a large Temperature
drop to keep the equation equal.
Under certain conditions, this would mean the water particles in the
air would freeze and block the Jet.
So the Jet is heated by coolant that is passed around the Jet via a Banjo
coupling.
This heating gradually cooks the oil and carbon and blocks this Jet.

Now then, with this Jet blocked, the oily fumes, at Idle, can no longer
pass through the Smaller Breather Hose. So they pass through the
Larger Breather Hose and through the Throttle Body and the IACV.

The oil starts to coat the internals of the IACV and build up until
they block the Air passages, thus restricting or stopping the Air flow.
Result? Your engine is starved of air and stalls.

So you can now see why cleaning or replacing the IACV will only be
a temporary fix and will just waste you time and money.

So how do you check for this? Refer to the following picture.



Disconnect the Smaller Hose from your cam cover.
Start your engine and let it Idle. Check for a suction on the Small
Breather Hose by placing your thumb on and off the end of it.
No suction? Your Breather Jet is blocked.

Continued......... Please do not add to thread.
« Last Edit: 26 February 2009, 11:53:03 by TheBoy »
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Grumpy

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Re: How To Clean Your 2.0L IACV and Breather Jet
« Reply #1 on: 02 November 2007, 12:49:03 »

Picture of Throttle Body and the 2 Jubilee Clips to remove
a section of Intake Trunking from the Throttle Body



Remove the Larger Breather Hose. (2 clips)
Remove the large black intake trunking that connects on to the Top
of the throttle body. (2 large jubilee clips)
Remove your IACV. (1 electrical connector and 2 bolts)

Follow the Smaller Breather Hose until you find where it connects
to the Jet, just below your throttle body, between the throttle
body and the engine.

Picture of Jet that the Smaller Breather Hose Connects to.



Use some long thin pliers to compress the ends of the clip securing the Breather
Hose to the Jet, and use a flat bladed screwdriver to gently lever the clip back  
along the Hose away from the Jet that it connects to.
 
Now put the pliers around the clip and gently wiggle the Hose whilst levering
between the end of the Hose and the Jet with a flat bladed screwdriver
until you've removed the Hose from the Jet body. Don't try just pulling the Hose
off, as it may have stuck to the Jet and hardened and will probably break.

2 water pipes connect to a Banjo Joint that swivels about the Jet.
So you've no need to disturb the pipes. The Banjo, with the 2 water pipes
still connected, will just hang roughly in position when you remove the
Breather Jet.
There are 2 metal sealing washers either side of the Banjo, that seal when you tighten
the Jet into the Inlet Manifold below the Throttle Body. So don't lose or damage them
or you'll end up with a coolant leak.

Unscrew the Jet using a normal spanner, bit slow this, as it's a 'flat at a time' job,
and then you need to reposition the spanner.
Watch for the metal washer between the Banjo and the Inlet manifold as the
Jet unscrews. It will probably loosen and drop down off it's land and onto the Jet
as a gap opens between the Banjo and the Inlet manifold. If it does, loop a piece of
wire or cotton thread through it to stop it dropping out of sight into the depths
of the Manifold assembly before removing the Jet completely.
When you remove the Jet, ensure that you also have the other metal sealing
washer that fits between the Jet nut that you've been unscrewing and the Banjo
coupling.
You may get a little coolant flow from the Banjo when you remove the Jet, but
we're only talking an egg cup full here.  
 
Once out, I don't drill the Jet, I stand it on end and fill it with Carb Cleaner.
Let it soak and keep prodding it with something thin and pointed, like a darning
needle or something similar. As the carbon softens, you will eventually break
through, and then you can clean it out easily.
Remember that the Jet is shaped inside like an Hour Glass Eggtimer.
So it narrows right down to 1.6mm in the centre. So don't try and
push anything through it larger than this.
 
These Jets are calibrated to give the correct flow through at Idle. If you drill it
and get it off centre or the wrong size, you will widen the jet and then get the
incorrect airflow through into the engine at Idle. This will give you an unmetered
airflow, similar to a split vac pipe.
 
When you refit it, ensure that the metal sealing washers are seated correctly
either side of the Banjo joint, and sitting correctly on the Breather Jet lands.
The one in between the Banjo and the Inlet manifold will keep trying
to slip off. So I found it useful to hold it in position with a small flat bladed
screwdriver, on the Jet Land and against the Banjo coupling, whilst tightening
the Jet back into position.
 
As the Jet starts to bite into it's final position against the Inlet manifold, the friction
between the Banjo and the sealing washers will try and spin the Banjo in the
direction of tightening. So wedge a large flat screwdriver blade between one
of the Banjo water pipe connections and the Fuel manifold to hold it in position
during the final tightening. This will hold the Banjo and pipes in the correct
position and not put them under a strain when fully tightened.
 
Clean out the small Breather Hose.
Wiggle the Breather Hose back onto the end of the Jet, and then refit the clip,
again using the long thin pliers and screwdriver to aid positioning it correctly.
 
Don't forget to check for any water leaks from the Banjo when you run the engine.
Best to find out now rather than 100 miles up the motorway when you start
overheating due to lack of coolant.
Check and adjust Coolant level in Header tank as required.

Clean out the Large Breather Hose.

Continued........Please do not add to thread
« Last Edit: 26 February 2009, 11:53:47 by TheBoy »
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Grumpy

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Re: How To Clean Your 2.0L IACV and Breather Jet
« Reply #2 on: 02 November 2007, 12:52:22 »

Now we come to the IACV.
Have a look at the following pictures. The exploded view was kindly
provided by 'Abiton', who took one apart to see what made it tick.







The Inlet hole to the IACV is deeper than the Outlet. This is because
it provides air to the hidden air passage ways that pass to the end
of the IACV and to the second of the Twin Valves.
Look at the exploded view and you will see the 2 kidney shaped slots
that pass through the valve to pass the air to the second valve.
It's these airways and the second valve that get coated and blocked
with oil.

Undo the 2 screws that secure the electric motor to the valve,
and slide the motor off the valve stem.

Fill the valve with carb cleaner or fuel. Ensure that you pour
or spray it down the inlet hole, so that it passes through the
hidden airways and down to the second valve down by the
flat end of the valve. Allow it to soak and agitate it by covering
all 3 holes (gloved fingers and thumbs works for me).
Stand it on its flat end with the inlet and outlet holes facing you.
Tilt it slowly away from you so that the cleaner and muck flows
away from the second valve, washes out the hidden airways, and
out via the end where you've removed the Electric Motor from.
This will ensure that you don't wash all the crap down to, and
block, the second valve orifice.

Repeat until clean and then thoroughly dry.

Put a little electric lube or vaseline on the shiny bit of the valve stem
that protrudes into the motor. Do not lube any other part of the valve!!
The only contact point on the valve is the stem that protrudes into the
motor. Any lubing anywhere else is not only pointless, but will dry onto
the valve body and act like sticky flypaper that will attract crud like ****
to a blanket.

Reassemble the valve. Spin the valve stem until you can see a small hole
in the valve plastic coating in the hole nearest the flat end of the valve.
Put a thin 'Podger' in the hole and draw the valve back towards the flat end
against the spring pressure.
When you release the 'Podger' from the small hole in the valve stem check
that the spring pressure returns the valve fully back towards the motor end.
Check this by trying to move the valve towards the motor end. There shouldn't
be any movement.
 
If it doesn't return, repeat by cleaning and lubing the valve stem inside
the motor bit until it does.

If you wish, clean your throttle body. That has already been detailed
by other good folk on this forum.

You may also wish to remove and clean the other breather hose, on the
back passenger side of the engine, that connects between your crankcase
and cam cover. This has also been covered on this forum. Some also
fit a flame trap mod to this hose.

When you refit everything, ensure that you use a new gasket between
the IACV and the throttle body. If this gasket leaks internally, or draws
in air externally, your ECU will not be able to control your IACV.
This will give all sorts of defects from, high, low, or fluctuating RPM.

Now enjoy your smooth idling, non stalling, Omega limo!
Hope this helps, but remember that this is just one reason
that can cause your Omega to stall. A failing Crank Sensor, for instance,
can give similar cutting out symptoms.
« Last Edit: 26 February 2009, 11:55:14 by TheBoy »
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TheBoy

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Re: How To Clean Your 2.0L IACV and Breather Jet
« Reply #3 on: 26 November 2007, 08:40:55 »

The following pictures were kindly provided by mkaminski100.
They show the Breather Jet removed and the small size of the internal jet that you are unblocking.



« Last Edit: 23 February 2009, 09:22:26 by Mark »
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Grumpy old man

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Re: How To Clean Your 2.0L IACV and Breather Jet
« Reply #4 on: 07 April 2008, 16:12:55 »

The 2 guides, used in conjuction, make excelent reading.
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