AE86 16V - Auxiliary Air Valve...

[jondee86]

All 16V 4AGE engines have an Auxiliary Air Valve (AAV) attached the underside
of the throttlebody (TB). The purpose of the AAV is to raise the idle speed on
a cold engine for better starting and faster warmup. It does this by admitting
extra air into the intake manifold when the engine is cold. The AAV contains a
water heated air valve controlled by the expansion and contraction of a wax
filled capsule. When the engine is cold, the valve is open. As the engine warms
up the water from the engine cooling system circulating thru the valve and
around the capsule heats the wax capsule. The capsule expands and gradually
closes the valve, reducing the amount of extra air entering the manifold.



When the AAV is operating correctly the cold idle will be around 2200 rpm.
This will drop to around 850-900 rpm when the engine is fully warmed up )if
the engine is running normally).

When the water side of the AAV becomes blocked, the cooling system water
can no longer circulate, and the engine will have a permanently raised idle.
If the warm idle remains above 1700 rpm the engine will start to cycle on the
fuel cut, and you will have the classic loping/cycling idle as if you were gently
revving the engine over and over again with the gas pedal.



To clean the AAV remove it from the TB and using a thin skewer, wire, knitting
needle, pipe cleaner (or whatever) work away at the water inlet and outlet
connections until the valve flows water freely from one to the other when you
hold it under a tap. Check the little rubber hose are clear also. The usual cause
of blockage in the AAV is rust particles or bits of silicone sealant from overdoing
cooling system repairs. Brake cleaner won't be much help to you. Once the AAV
is clean, put it back with a new o-ring and a new paper gasket available from
Toyota or included in any engine overhaul gasket set.

EDIT: Just to be clear, the arrow that says "Water Inlet" is pointing at the steel
tube, not at the little stub. Water goes up into the throttle body thru the steel
tube, and then comes back down thru the little stub and into the AAV.

Cheers... jondee86

[asnfro]

Like

[idreamofdrifting]

+1

[strmrdr23]

i'm having a similar symptoms but not only does it do that loping idle but rpms fluctuate from 1500 to 800 and then sometimes it just drops real low and dies. does this sound like AAV issue still?

driving is no problem, just idle. car is fully warmed up.

[jondee86]

If you get a normal cold start where the engine first runs at around 2200 rpm and
then tapers down to around 900 rpm when fully warm, the AAV is working as it should.

Have you checked to see that the TPS is set correctly ?

Cheers... jondee86

[strmrdr23]

I'm a total noob. Idk how to check tps. Lol. My issue is more that I have to raise my idle up to try and keep the car from dying. I've adjusted the screw to raise it but it doesn't seem to hold my adjustment if that's makes sense. Like it'll be up to 1200 (where I set it to) but as I drive it around, it'll drop to say 800 but then it's seems to be running rough at that point. Then I'll continue to drive it and the next time I come to a stop, the RPMs may drop to the point it just dies and when I start it up again it won't stay running.

[jondee86]

If you get a normal cold start where the engine first runs at around 2200 rpm and
then tapers down to around 900 rpm when fully warm, the AAV is working as it should.

First things first.... does this ^^^ happen ??

Cheers... jondee86

[strmrdr23]

it's close to that. in retrospect, i realize it's not so much my idle is the problem (sure it fluctuates and i've raised the idle a bit) but that was to try to combat the stalling. i've been researching some more and it may not be my IACV that's the issue but possibly my lightweight flywheel. the RPMs drop so fast when i come to a stop that it stalls the car. i have recently just installed a LINK ecu and i'm going to check with my tuner to see if that's something they can do to compensate for that rapid RPM drop when i'm coming to a stop. i'm able to mitigate the stalling by letting the RPMs come down gradually.

[jondee86]

OK... now the problem becomes a little clearer

Generally speaking, when you install an aftermarket ECU, you should also
install a electric ISCV (Idle Speed Control Valve) that the ECU can control to
provide extra air to the engine when required. This puts the ECU in charge
of adjusting the idle speed and does away with the need for the factory AAV.
The AAV can be disabled by disconnecting and looping the water hoses so
that the wax stat does not get hot, and the AAV stays OPEN all the time.

Having a light flywheel should not be a problem.

With an electric ISCV the ECU has the ability to control the idle according to
engine temperature and other factors, not only by adjusting the amount of
idle air but also by adjusting the ignition timing. It can easily catch and
correct the tendency for the engine to stall in a hot off-throttle situation
(such as when you catch a red light just after coming off the expressway).

If you have an ISCV installed, it should just be a tuning matter. If you don't
have an ISCV you should consider having one installed.

Cheers... jondee86

[jdm86gtz]

I came across this write up recently on how to completely strip the AAC valve and adjust it:
http://www.mr2.com/forums/threads/10453 ... adjustment
I haven't tried it yet as I will get someone to make up the tool required.

[strmrdr23]

OK... now the problem becomes a little clearer

Generally speaking, when you install an aftermarket ECU, you should also
install a electric ISCV (Idle Speed Control Valve) that the ECU can control to
provide extra air to the engine when required. This puts the ECU in charge
of adjusting the idle speed and does away with the need for the factory AAV.
The AAV can be disabled by disconnecting and looping the water hoses so
that the wax stat does not get hot, and the AAV stays OPEN all the time.

Having a light flywheel should not be a problem.

With an electric ISCV the ECU has the ability to control the idle according to
engine temperature and other factors, not only by adjusting the amount of
idle air but also by adjusting the ignition timing. It can easily catch and
correct the tendency for the engine to stall in a hot off-throttle situation
(such as when you catch a red light just after coming off the expressway).

If you have an ISCV installed, it should just be a tuning matter. If you don't
have an ISCV you should consider having one installed.

Cheers... jondee86

thanks for your reply, man!!! what's the diff between IACV and ISCV? any idea where i can get an electronic ISCV or recommend one?

I came across this write up recently on how to completely strip the AAC valve and adjust it:
http://www.mr2.com/forums/threads/10453 ... adjustment
I haven't tried it yet as I will get someone to make up the tool required.

I saw this yesterday too. thanks, man

[jondee86]

This is a 3-wire ISCV from a 20V 4AGE...



And this is a 2-wire Bosch ISCV...



Both of these can be bolted on or close to the engine and plumbed between the
airbox and inlet manifold. There are many other kinds as they are installed from
the factory on all modern cars, but the type with two hose connections are the
easisest to retro-install on older engines. Again I would talk to your tuner to
see what he recommends. ISCV = IACV.

Cheers... jondee86

PS: Understand that the ECU will get severely pissed off if it is trying to control
idle with an ISCV and the AAV is also leaking air into the intake manifold !!!

[strmrdr23]

jondee86, you're the man! lol. so i just look for an electronic (remote?) ISCV that is compatible and then block off the mechanical AAV. seems easy enough. I'll start another thread if i have more questions and not thread jack this one no more. thanks again.

[strmrdr23]

i've found this universal one by haltech - http://www.carid.com/haltech/idle-air-c ... 20310.html

and this kit too - http://www.carid.com/haltech/ecu-output ... 20300.html with this http://www.carid.com/haltech/ecu-output ... 20302.html

the latter has 4 wire stepper motor but my ecu specifies "Solenoid or Uni-polar 6 terminal stepper only."

[jondee86]

Both of those Haltech valves look like 4-wire steppers. And the reference to a "4 Port"
valve seems strange... there is no need for a 4-port valve Maybe some copywriter
got confused with 4-wire as the valves look like 2-port items to me.

Digging a bit it seems that Haltech resort to the 'ol faithful Bosch solenoid valve when
4-wire stepper control is not available (Idle Air Control Valve Bosch BAC/PWM 2 Port, 2 Pin).



AFAIK the Bosch valve is factory fitted to a wide range of cars, so they should be easy
enough to find in the junkyard. They are some kind of solenoid (rotary probably) and
suitable for PWM control. There are 2 and 3 wire versions, and I guess that the 3-wire
version has two windings, which should make it faster acting ? I don't actually know
much about them, other than the fact that they are widely used (I use the Toyota 20V
3-wire PWM rotary solenoid ISCV which is cheap as chips in NZ).

Cheers... jondee86

[strmrdr23]

ok, so i found basically the same thing in my research yesterday (hey, it was slow at work!). i was just confused as the openings on the bosch valves were so large. they appear to be pretty readily available on eBay and such...going to pick one up soon. Thanks again, jondee!

[SgtRauksauff]

I just took a piece of aluminum plate and some FIPG, and sealed off the whole AAV altogether. Solved my racing idle problem, and helped get rid of a couple more hoses. HOWEVER, this was for a car that is not DD'd, but rather mostly for motorsport use. So I'd just sit in it and use the foot feed to modulate the idle speed until warm enough to idle properly on its own.

After I fixed the racing idle issue, I would get a wierd rhythmic surging idle, which turned out to be TPS adjustment. Flywheel weight shouldn't be too much of an issue (I have an Illegal Garage lightweight) but I have noticed (in other cars as well) that if TPS is misadjusted, and I closed the throttle plate quickly, sometimes the car would stall. That bosch looks identical to the one on a couple of the Volvos I've had, and I've seen them on Saabs as well, so if you're looking for donors in a JY...

[strmrdr23]

I just took a piece of aluminum plate and some FIPG, and sealed off the whole AAV altogether. Solved my racing idle problem, and helped get rid of a couple more hoses. HOWEVER, this was for a car that is not DD'd, but rather mostly for motorsport use. So I'd just sit in it and use the foot feed to modulate the idle speed until warm enough to idle properly on its own.

After I fixed the racing idle issue, I would get a wierd rhythmic surging idle, which turned out to be TPS adjustment. Flywheel weight shouldn't be too much of an issue (I have an Illegal Garage lightweight) but I have noticed (in other cars as well) that if TPS is misadjusted, and I closed the throttle plate quickly, sometimes the car would stall. That bosch looks identical to the one on a couple of the Volvos I've had, and I've seen them on Saabs as well, so if you're looking for donors in a JY...

thanks, sarge. i think this bosch joint is ubiquitous on VW as well. I'll fiddle with TPS next. woot.

[aceforever]

That bosch looks identical to the one on a couple of the Volvos I've had, and I've seen them on Saabs as well, so if you're looking for donors in a JY...

Time for me to hit the JY again . Or perhaps I can order one online. Anyone have part numbers off hand?

[aceforever]

Found some great information here:

http://www.adaptronic.com.au/idle-valve-wiring/

I've looked at the Haltech E6X manual. They call the AAV, BAC (bypass air control). And they do support rotary 3 wire AAV w/ something called a BAC Slave which provides inverse voltage of BAC. It's pretty cool.