16v 4age idle issue (prolem found)

[andyling]

It has a leaky injector seal.

Hi guys

I got an issue here can't solve, see if someone can give me a hand on this.

I have replaced the engine in my ae86, every thing is stock except 2nd gen 16valve block and head. all ok except idle jumps up and down when the car is warm.

I have discovered that the air thermostat idle valve ( auxiliary air valve AAV) is stuck open, as I can put the finger on the air by pass hole, the rpm immediately drops ( not low enough).

So here is what I am at now.
Idle adjust screw is all the way down and blocked AAV air inlet. Timing is set to 10" at diagnostic mode, but jumps to 17-20 at normal mod at 1400rpm

Do I really have a bad AAV? ( inlet and outlet water hoses are hot while running)
What else do I have to check?

http://club4ag.com/forums/viewtopic.php?t=12013

[jondee86]

There are two holes inside the front of the throttle body. One for the idle air by-pass
screw (for adjusting idle speed) and one for the AAV (supplies extra air for cold start).



To be clear, are you saying that you have completely blocked the AAV port and when
you block the by-pass port as well, the idle still does not drop below 1400rpm ?? If that
is the case you must have a vacuum leak somewhere that is letting extra air into the
engine. Have you checked that the throttle butterfly is shutting completely ??

Both hoses getting hot means that coolant is circulating thru the valve, but does not
prove that it is working. If it is working, then your cold idle should be around 2200rpm
dropping back to normal as the valve heats up and closes.

Cheers... jondee86

[andyling]

Thanks Jondee86, Yes, the injector seal (insulator) had massive leak. AAV is still worn tho I believe.

Waiting for both parts anyway. other than that car idles fine.

[xsspeed]

Only reason for coolant circulation is defrosting of throttle body IIRC, you can block/bypass/whatever

[jondee86]

The circulation of coolant thru the throttlebody may help prevent the throttle
icing up in much colder climates than NZ. However, its main purpose is to heat
the wax capsule that operates the AAV to assist with cold starting.

Early 4AGE's (bluetops) did not have an electrically driven ISCV as is found on
20 valves engines. So the thermostatically operated AAV is open when cold to
let extra air into the engine to aid starting and prevent stalling by raising the
idle rpm . As the engine warms up the wax capsule expands and gradually
closes off the extra air until the engine settles to normal idle when it reaches
operating temperature.

While it is true that the engine can still be started if the AAV is deleted or
blocked off, on cold mornings it will be prone to stalling unless the throttle is
tickled until the engine starts to warm up. Idle speed will be low when the
engine is cold and high when the engine is hot, meaning that the idle speed
will be a compromise between too low and too high.

So while the AAV system is outdated by today's standards, it is generally very
reliable and trouble free if the cooling system is properly maintained.

Cheers... jondee86