4AGZE Idle Issue *** FIXED *** Read for details...

The Fix
 
So many 4AGE/AGZE owners appear to have idle issues and I reckon not many actually find the real cause.
A high/rough idle is not a problem, it's a characteristic of a problem. The first place many look or just blame is the wax pallet idle control valve. This can be a cause of a idle issue, but there are other things that can cause idle. My AGZE had a rough/high/oscillating idle and I replaced the ICV without any improvement. I could set the idle at a sufficiently high RPM to stop the stalling on throttle release, but it was no where near Toyota Perfect (TP). Also, I wound the screw out on the AFM bypass chamber to alter the AFR on idle (the only reason the bypass chamber exists is for idle mixture control). So it appears to be running ok (ish) - but not TP.
 
The often thought about, but never really diagnosed vacuum/intake leak looked like being a culprit, but how to test? - The standard method of spraying Carby Cleaner all over the place listening for a change in engine note is pretty ineffective on these engines. The process to find all leaks is so simple and it only takes a few minutes.
 
Remove the air cleaner from the firewall entry point and block that off (I used a 500ml paint cup over a bit of 3"silicon hose to seal it and a hose clamp.
 
Remove the vacuum hose from the charcoal canister and connect up a vacuum/pressure gauge (this will allow you to measure the pressure of the intake system) - then remove the AC idle up hose from the intake and block the hose off. Then connect compressed air (through an air trigger) to the AC Idle up port. You can now pressurise the entire intake system to about 10PSI.
 
You will need a spray bottle with soapy water to spray on joints etc at this will bubble away on leaks.
 
When I did this I immediately heard escaping air - from no3 injector, the rubber seal between the injector and the head was leaking (bad too)... 10PSI of system pressure went to 0 in about 2 seconds.
 
I remove the fuel rail and injectors and replaced all O rings and seals (3 on each injector) then put it back together and repeated the processes. This time, air was leaking out the new silicon connector hoses between the top of the intake and the intercooler - they were slightly loose but I thought a good hose clamp would sort that out - WRONG!... I replaced these with the factory rubber ones and repeated the test.
 
Now the only leak is a very slight leak from the throttle body shaft, These cannot be serviced but I decided to leave it as it's now taking about 4 minutes to go from 10PSI to 0PSI - that leak is minimal.
 
REMEMBER To remove the block on the intake -
 
I started the car, immediately the difference was noticeable, a smooth idle - and that's before I had to re-adjust all the things I have played with back to standard. Once back to standard the car starts and idles at 1200 RPM before dropping back to 800 at 180 degrees F.  TP !
 
FYI - The AFM has a number stamped on it that indicates the factory calibrated setting, the number refers to the distance the top of the adjustment screw is from the top of the casting.
30 = 13mm, 26 = 12.6mm, 24 = 12.4mm  So the AFM can be set back to this.. Note this screw has no effect on the operation of the AFM, it's there for the bypass chamber air flow control for idle, this figure should never alter from factory and so the screw should never need altering (IMHO)
 
.. Hope this helps those with dodgy idle ...