High idle, probably broken IAC, questions

[fixkick]

Update: IAC is leaking.

I did diagnose this bit differently. I did not want to use clay incase it would get inside my engine it turns real hard when it burns. And I wanted to avoid taking the TB out.

So here was my method. Create a batch "magic play dough" (recipe from near kindergarden).

1 dl = 0.422675284 US cups

1 dl of wheat flour
1/2 dl of salt
1/2 dl of cool or cold water
1 teaspoon of any food oil

Mix 5 minutes and its done. This amount would suffice for about 10-20 IAC ports, but its hard to make very small batch and its cheap.

If dough is too grainy, add water. If its too sticky add flour. If you cant get it not sticky like me add a few droplets more oil.


WARNING: This thing will eventually harden out and you need to hack it out of the port someway if you do not remove it until it dries completely. Tho it will take probably hellishly long to harden when its inside the IAC hole and inside almost tight plastic wrap.

(Original idea for the thingy is that kids can make pots and animals from it and then you can burn it hard in oven bit like you do with clay).


the best clay is not clay, it is called electrical mastic,, any electrician calls it monkey poop , spelled Monkey sh!t. it never gets hard and is super stiff and sticky, and will not suck in. done right. (a true art that , no?)



TRY1: Failure

Then I opened the IAC cover and put some magic dough into double layer plastic wrap and suffed the port, closed the cover and startup. 2 minutes ok and then rpm rose -> I shutdown engine. Plastic had failed due to vacuum and very small amount of the dough went to engine.

I removed dough. closed IAC cover in original setting and kept running eninge until white-gray smoke (and strange burning smell ended). IE.. dough burned trough engine. Let it run for quite a while after that to excrete any possible salt (if it had even had time to dry and crystalize as it dissolves in the dough).

Thanks for your words here, all,  and details, this is not easy to do this, takes great care to diagnose the guts of any TB.  (best is in a pan of hot water, on car super hard to do)
 

TRY2: Success.

1) open IAC cover
2) Line the huge vacuum port with extra strong aluminum tape. After that create 1-2 extra full rounds of alu tape lining. ( boy that is smart)
3) Insert double plastic wrapped dough into the IAC hole
4) close IAC cover with gasket.
5) Start.. idle rpm was 200-300 BINGO (by the gauge, which is unreliable at so low). Anyhow apply throttle to keep about 1000rpm until water heats and STAT opens.
but IAC is open cold , below 150F it is open the IAC and normal. what matters is hot.

And after that it kept running bit waving between 800-1000rpm  (my ISC is dead, diagnosed long ago, cant find replacement for the 89/90 thingy).
The ISC unplugged hot, the IAC closed like you did the engine can nor run at all.  ever, there is no air, but super tiny past the TV valve.
Keep in mind the ECU knows to wakes   up isc ISC as IAC goes closed.
Id you do the TV valve calibration,  set at the TV stop screw on 89/90 that is idle duty cycle settings for ISC , just screw it screw until the iSC wakes up and regulates at 800 rpm
then turn it in CW one more turn,

your ISC is bad or not calibrated,
make sure the gasket under ISC is not a wreck , has 2 holes not 2 cut to make one as some do when engine stalls cold.  
many folks cut the iSC gasket up to hide a dead IAc STOCK CLOSED FOREVER. (LIKE your previous owner may have had and done)
but your IAC works mostly.

id look at the ISC very  closely for DAmage of its gasket first. and see if coil is at 6ohms DCR  DC resistance, 2 times what 91+ reads. years.
the with no voltage to ISC see if it can close. as it must.
the ECU only opens it with modulated power. to it (PWM methods)


Anyhow.

What do you suggest for casting the hole shut? (I WOULD ONLY DO THIS (NO SPARE TB) In a way  that is regressive later (undo -able)
unscrew the TV stop screw CCW. see RPM fall. must, unless TV is 100% closed and that is not correct if closed on all 89/90s.



I was thinking I will apply aluminum tape again (to avoid any stuff going into engine) and then either use epoxy glue or chemical metal to block the IAC vacuum suction to TB and let it set for 48 hours or so.
try alum tape,  use high grade HVAC duct tape from 3M and then put plaster of Paris inside there,


Then I will apply a T-junction with rogue hose and moped's fuel valve into the cabin to have a bleed air valve for cold idle boost. (yes this can work and use any valve to calibrate it and one more to open and close for quick action cold. (or and home made orifice, calibrated in series for 1000 to 1500 rpm cold.
you will not be the first here.... others can not find the iSC sold or do not like the $250 price tags . then learn the ISC driver transistor in the ECU is blown.

good luck to you and thanks alot for sharing!!!!!! cheers.