High idle when warm 2zz-ge: Stuck IACV?

[fielderz]

I have a 6 speed manual 2001 fielder Z wagon, as per my username, which I am thoroughly impressed with so far! Its fun to drive, practical and still feels and drives like a brand new car (it seems to me) at 102000km on the clock.
The only small issue is that when warm it idles at 1800-2000 rpm, when cold it idles perfectly at about 950 rpm.
I've searched online and found a bit of info, but nothing great, the basic jist was either a gummed up throttle body or a failed idle air control valve.

Here is what I did, which I hope will be of help to anyone else with a similar issue with the ZZ series of engines, which should all be pretty similar.

Before setting out, I recommed you acquire the following parts:
2x M4 20mm screws in your choice of head- recommend hex/allen head.
3x M5 20mm screws in your choice of head- recommend hex/allen head.
3x M5 washers
1x Throttle body gasket.

The IACV is made up up a small black plastic, electro-magnetic actuator, and a larger aluminium body containg a small rotating sort of barrel valve bolted to the main throtle body. Annoyingly the black plastic actuator is secured to the IACV body using two 5 point torx/star drive (M4 20mm) screws, making removal difficult. The IACV body is secured to the throttle body with 3 phillips head (M5 20mm) screws which are extremely hard/impossible to remove in place.
At this point I decided to remove the throttle body assembly, which wasn't particularly difficult and did not require any special skill or tools, with the worst part being the removal of the two coolant lines which were pretty stuck on, by the way the throttle body bolts are the perfect size to plug those lines temporarily haha.
Once off, I checked throttle plate operation- which was fine: closing and sealing well, not particularly gunked up or anything. I was actually pretty impressed how relatively clean it was, but it still benefited from a good clean up before reassebly.
Now it was time to remove the IACV for a look.. those phillips head screws are mighty hard to crack, and their heads are pretty soft... I tried penetrating lube, tapping and heating the IACV as much as I dared etc, all to no avail. I had also knocked together a little holding jig out of some scrap four by two so I could bear down with max force. At this point I decided to get nasty and just slot the screw heads with a hacksaw. Then, after tapping the blade of my biggest flathead screwdriver into the new slots, the screws came out easily. This worked well for two, but the third isn't very hacksaw accessible and I had to twist the IACV body with the first two removed to loosen this last one.
Now the ICAV is separated from the throttle body. (yuss!)
Now you can check out the gunk/gummyness situation, however you still can't do a hell of a lot, I have a link to the IACV diag. proceedure below, but I would recommend cleaning and freeing up the IACV first.
At this stage I wanted to remove the small black electro-magnetic actuator to make freeing it up the IACV a bit easier, but those 5 point torx screws make it pretty tricky.. so out came the hacksaw and flat head screwdriver again, which made short work of those little buggers. Now the actuator can be pulled off, it is magnetically attached to the shaft too, so needs a little tug to come away.
Now the IACV valve barrel can be spun right around and easily cleaned and freed up. Mine was a bit stuck in what was probably cold idle position, likely causing the high idle when warm. Mine cleaned up beautifully, and the movement is now free as a bird.
At this point I was still unsure if the electro-magnetic actuator was working ok, below is the link to the diagnostic proceedure I used to check the IACV. I temporarily reasembled the IACV and plugged the throttle body TPS back in to do the below. (For referecne to others, the IACV needs to be removed from the throttle body to observe the movement of the IACV barrel.)
http://www.autozone.com/autozone/repair ... 3f80380339

The proceedure directs you to remove the ECT sensor plug, however I found that the IACV only moved when it was plugged in, I'm guessing this was due the car engine being cold at the time.

So my IACV moved like it should and proved to be ok after cleaning, which I was pretty happy about. Now after everything is all cleaned up and checked, its time for reassembly.. Now I wasn't keen on using my now butchered screws haha, and wanted to replace with something nicer and more serviceable. I already had some stainless M5 20mm screws, with much chunkier heads, so I could do the final attachment of the IACV body to the throttle body on the workbench, which is definitely better than doing in place. I had to attach the black plastic electro-magnetic actuator to the IACV body with the original screws temporarily though, but these are super easy to get to in place- so wasn't the end of the world.
I then put everything back together in the engine bay, a note here- the throttle body gasket is a steel one and due to it being mint and my being a semi poor student I reused it (I also did not expect to be removing the throttle body at the outset), maybe you want to get a new one before embarking on this exercise. Mine seems to be working fine with no leaks though.
Now it was time for a drive to the fastener store, and at the same time, to see how she idles now when warm. I drove the 10 mins or so to EDL in Dunedin, which was enough to get the enginewarm enough to check the warm/hot idle, it was much lower- too low in fact (the IACV electro-magnetic atuator is adjustable- I just tweaked it when back home). I bought my two M4 20mm stainless hex head screws (the guy actually gave them to me for free, nice ay!) and I was away. I swaped out the old screws for the new and tweaked the idle to about 950 rpm and I was done.
I'm pretty stoked how it all worked out, its now a lot easier to service if the IACV gets gummed up again (no need for throttle body removal, and I can easily tweak the idle if I want to.
As a final note, the IACV seems to be a pretty reasonable design even if prone to sticking, the magnetic coupling of the actator to the barrel valve means it shouldn't burn out the actuator as it likely would in the case of the barrel sticking in a mechanically coupled design, so I would definitely try cleaning before replacing.

Keywords to help others searching: 1zzfe 1zz-fe 2zzge corolla fielder runx allex E120 idle high low adjust

[fielderz]

Ps. This would also be a good time to clean/replace the PCV valve (located on the throttle body end of the rear cam cover near the oil fill cap), while the engine cover is off. Again, me being a semi poor student, I just remved and cleaned mine, it wasn't to bad, slight sticky but still opening and closing. A bit of CRC and a bit of shaking and it was as good as new.