High idle, probably broken IAC, questions

[jwunsch]

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).

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).

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.
3) Insert double plastic wrapped dough into the IAC hole
4) close IAC cover with gasket.
5) Start.. idle rpm was 200-300 (by the gauge, which is unreliable at so low). Anyhow apply throttle to keep about 1000rpm until water heats and STAT opens.

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).

Anyhow.

What do you suggest for casting the hole shut?

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.

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.

[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.

[fixkick]

16 ounces, of love this stuff.

https://www.lowes.com/search?searchTerm=...+duct+seal

aka MS or monkey do do..

used in electrical boxes to prevent water from using electrical conduits as drain , I have seen horror damage from water doing that , even seen 400vac panels blow things to hell and all things down stream from that event. huge damage, like 100s of computers blown up and more.

[fixkick]

What's cool later is it comes back out easy later.
not sure how it likes 180f me, but seems it is ok,.
the box says, not slump
at 350F, sure as heck. super good and super stiff it is and super super sticky, like TAFFY like.

[jwunsch]

Hi,


Thanks for the idea of using plaster of Paris. It was quite easy to get there even the TB still fitted on the car. I also did a test plastering to a base of this kind of candle. It was easy enough to get the plaster to split and then dig it out.

Tuikku®

Basically hardest part was to get the first piece of aluminum tape to block the "3 pm" hole. I wanted to get as long as possible strip of tape there so that it has a lot of area where to stick. I managed to get about 1" continuous piece there.

All the other pieces where around 1cm which around 0.39xx". So I kept sticking them there to try to block about everything. (3M scotch aluminum tape)

I did notice on the last test run that after heating up the aluminum tape sticks very well on the IAC hole, but its still semi easily removable. Hardest part is that my fingers wont fit there easily.

   

Then another layer with the extra strong (3M scotch) duct tape. At least it creates isolation layer to the alu tape.. so I guess that if I have to take the plaster out, I can get it all out before I will have to take the alu tape out. So should be able to do that without getting any of the stuff into engine.


At this point I did a test startup. After dashpot stopped boosting throttle the RPM set so slow that the tachometer some times show 0 sometimes round 200.. ie it was so low that tachometer did not always even work. So best guess is its blocked enough even with tape.


   


And finally some plaster.

Note I did take the picture before doing some cleanup. That stuff is easy to clean up with wet tissue or some paper like that. Cleaning the bold whole was pretty easy with needless syringe and water. After that I did drove the bolt into crew hole and took it out to be sure I forced it clean.

   

So I am guessing that tomorrow when all that has set, I need to just make a T-junction to any of the vacuum lines and test startup with "bleed air on" and wait for warm up and block the bleed air to verify this DIY choke works.



All in all it took me 45 - 60 minutes to do this. The first testing with that play dough took 1.5 hours including creating the dough.. so 2.5 hours all in all.

And I would say that you can skip the play dough crap and just use alu + duct tape to block everything in 15-30 minutes to verify if the IAC leaks.

If cold RPM is 400RPM or below I would say it blocks enough. Then just warmup with pressing a throttle to keep RPM around 1000 until STAT opens and see where the idle stabilizes. I did wait about 10 more minutes after STAT opened to be sure I see where it stabilized. Then shutdown and restart after 5 minutes to see it still works. Saves huge amount of effort if one does not need to actually remove whole TB.

[jwunsch]

Update: All good and working fine enough for vehicle inspection. Thanks fixkick for help and ideas!



Idle fixed. Took a moment to figure out where I should place my T-junction and run the hose to cabin. After a few tries I found it.




   






Also I found out that on right side of the firewall there were several unused places to run big hoses trough the firewall so I ran my hose there.





This is temporary solution. I had some old hose, but its bit too short. Also I need to find a valve but its bit hard for such small diameter hose and then replace this with longer hose and run it to driver side with the valve.



   






Tested cold and hot idle with hose open / plugged.







Cold closed: 0-200 RPM (according to tacho)



Cold open: 2200 RM


Hot closed: 800 RPM lights off, 600 RPM lights on

Hot open: 2500 RPM.. so not too high if one forgets to plug it. Probably not every nice to drive, especially with any AT box.



(Note temp gauge shows pretty low, probably the sensor is going bad. Its actually 88C where my STAT opens. ).

   

[jwunsch]

Update:

Very shortly after experimenting with golf tee I moved the hose on driver's side near driver's right knee and put a moped's fuel valve at the end of the hose to be able to tune the vacuum leak and have RPM control.

cold 200-2200 (fully closed - fully open)
hot  800-2500 (fully closed - fully open)

Note a needle valve would be a lot better for selecting RPM as its designed for gasses, this valve is for liquid so the whole tuning range is around 2-3 degrees of rotation. Bit hard to tune, but it does what is needed.

   

[fixkick]

Update: 1991 Vitara MT, 2 door, G16a, 4wd.

Very shortly after experimenting with golf tee I moved the hose on driver's side near driver's right knee and put a moped's fuel valve at the end of the hose to be able to tune the vacuum leak and have RPM control.

cold 200-2200 (fully closed - fully open)
hot  800-2500 (fully closed - fully open)

Note a needle valve would be a lot better for selecting RPM as its designed for gasses, this valve is for liquid so the whole tuning range is around 2-3 degrees of rotation. Bit hard to tune, but it does what is needed.

wow, thanks for sharing all that data.  nobody has done this and posted the results. for building a fake,IAC valve, due to stock valve IAC stuck.(dead or weak)
that gas line valve is prefect. and easy to find too.

the dash gauge water temp uses its own 1 pin sensor and is not used for EFI , not used at all for the ECU for fuel mixing.

nice work and good luck for inspecting, get car hot, turn new valve for 800 rpm and bingo.
as you turn the valve , the ISC will kick in and do RPM controls HOT. to 800. (regulated ISC mode) hot.

i see yours did here. hot >>>> 800-2500 (fully closed - fully open)
 
the 2500 is because your  air leak is more than the ISC can control. 

try 1500 rpm cold see if when hot the ISC wakes up at 150F and goes to 800 like it should.


best wishes and cheers to you !


wow I missed your post before with super nice IAC packing job to take it off line..(leaking bad hot)  great photos those, and the method is perfect.
any method that can be Regressed easy  is best.  (blocking the base gasket also kills the air bleed in top of air horn, and is best to keep that working)

[jwunsch]

Update: 1991 Vitara MT, 2 door, G16a, 4wd.

Very shortly after experimenting with golf tee I moved the hose on driver's side near driver's right knee and put a moped's fuel valve at the end of the hose to be able to tune the vacuum leak and have RPM control.

cold 200-2200 (fully closed - fully open)
hot  800-2500 (fully closed - fully open)

Note a needle valve would be a lot better for selecting RPM as its designed for gasses, this valve is for liquid so the whole tuning range is around 2-3 degrees of rotation. Bit hard to tune, but it does what is needed.

wow, thanks for sharing all that data.  nobody has done this and posted the results. for building a fake,IAC valve, due to stock valve IAC stuck.(dead or weak)
that gas line valve is prefect. and easy to find too.

the dash gauge water temp uses its own 1 pin sensor and is not used for EFI , not used at all for the ECU for fuel mixing.

nice work and good luck for inspecting, get car hot, turn new valve for 800 rpm and bingo.
as you turn the valve , the ISC will kick in and do RPM controls HOT. to 800. (regulated ISC mode) hot.

i see yours did here. hot >>>> 800-2500 (fully closed - fully open)
 
the 2500 is because your  air leak is more than the ISC can control. 

try 1500 rpm cold see if when hot the ISC wakes up at 150F and goes to 800 like it should.


best wishes and cheers to you !


wow I missed your post before with super nice IAC packing job to take it off line..(leaking bad hot)  great photos those, and the method is perfect.
any method that can be Regressed easy  is best.  (blocking the base gasket also kills the air bleed in top of air horn, and is best to keep that working)

Thanks hope that someone having same problems can use this thread to sort out IAC problems. Also my goal here was to try to achieve debug and possible fix for the IAC without removing the TB from the car. I had tested everything else except IAC and checked the TB gaskets.


I have previously diagnosed by ISC being dead too or then impaired by something (bad TV position?). It does absolutely nothing when I turn on head lights or high beams. Hot idle up pin reacts to defroster, but ISC does not.

My hot idle is around 650 with lights and blower. 600 with lights + high beams + blower + seat warmer. 800 when all lights and blower off. Feels like someone has tuned it to 800 on that setup.

Vehicle passed inspection 3 weeks ago. I just forgot to update the valve pic here and remembered it due to the "1989 screamer" thread.

I do not care the hot idle not being modulated as it does not affect my driving at all. Oil pressure is ok enough (light off), battery is charged even on such low RPM and engine never stalls even if I step on clutch and lift throttle suddenly during driving.

Ie the only pain it causes is that it does not keep 800 RPM. But here for pre 92 or 93 cars the emission spec is pretty easy. Certain emission leves & RPM <= 1000.

Newer cars will be tested idle and high RPM and for diesels box on neutral a engine acceleration from idle to max RPM on full throttle to see how much smog an particles they do.

[fixkick]

Update: 1991 Vitara MT, 2 door, G16a, 4wd.

Very shortly after experimenting with golf tee I moved the hose on driver's side near driver's right knee and put a moped's fuel valve at the end of the hose to be able to tune the vacuum leak and have RPM control.

cold 200-2200 (fully closed - fully open)
hot  800-2500 (fully closed - fully open)

Note a needle valve would be a lot better for selecting RPM as its designed for gasses, this valve is for liquid so the whole tuning range is around 2-3 degrees of rotation. Bit hard to tune, but it does what is needed.

wow, thanks for sharing all that data.  nobody has done this and posted the results. for building a fake,IAC valve, due to stock valve IAC stuck.(dead or weak)
that gas line valve is prefect. and easy to find too.

the dash gauge water temp uses its own 1 pin sensor and is not used for EFI , not used at all for the ECU for fuel mixing.

nice work and good luck for inspecting, get car hot, turn new valve for 800 rpm and bingo.
as you turn the valve , the ISC will kick in and do RPM controls HOT. to 800. (regulated ISC mode) hot.

i see yours did here. hot >>>> 800-2500 (fully closed - fully open)
 
the 2500 is because your  air leak is more than the ISC can control. 

try 1500 rpm cold see if when hot the ISC wakes up at 150F and goes to 800 like it should.


best wishes and cheers to you !


wow I missed your post before with super nice IAC packing job to take it off line..(leaking bad hot)  great photos those, and the method is perfect.
any method that can be Regressed easy  is best.  (blocking the base gasket also kills the air bleed in top of air horn, and is best to keep that working)

Thanks hope that someone having same problems can use this thread to sort out IAC problems
. Also my goal here was to try to achieve debug and possible fix for the IAC without removing the TB from the car.
I had tested everything else except IAC and checked the TB gaskets.


I have previously diagnosed by ISC being dead too or then impaired by something (bad TV position?).

It does absolutely nothing when I turn on head lights  (only on 89/90 USA) or high beams. 80/90 only
Hot idle up pin reacts to defroster, but ISC does not. (heater blower, = defroster???) or rear glass of car resistor heater defroster?

91 does only dash blower in heater, idle up, and PS overload, (and rear glass heater only if fitted and does AC idle up if factor AC is present and working.
All iDLE ups are hot idle only, and  only work if hot engine, not cold.
idle ups are all ECU to ISC modulation methods called PWM.
IDLE UP MODES. FAIL
IF , NOT HOT ENGINE, 180F (common)
ISC clogged in side or coil inside open 
idle up pins into the ECU dead. (sensors for that wrong)
the TPS idle pin stuck at 5vdc ( means TPS is bad or just not calibrated using the factory TPS calibration that ends with TPS idle pin at 0v. (dask pot disabled)
Dash put stuck extended. hot idle. well this must be cured.
TV valve set wrong . stop screw. wrong on 80/90 but on 91+_ USA, it is set closed. and has bleed air screw in the front top TB air horn..
If at any time the hot idle is not normal 800rpm (+-50) that means the ISC is dead or just  off line. if off line idle up fails too, (a dual failure that0
ISC will fail if IAC is bad, if any device in the engine allows air to suck in illegally (IAC too) the ISC will fail, or even HUNT. (wild Rpm changes as ECU hunts the ISC like mad for 800)

this OP post is 91, not 89/90 and in USA those are totally different ECU and idle controls, for sure Idle up not the same.

My hot idle is around 650 with lights and blower. (hot or cold? engine) ISC only works HOT.
600 with lights + high beams + blower + seat warmer. 800 when all lights and blower off.
Feels like someone has tuned it to 800 on that setup.

Vehicle passed inspection 3 weeks ago. I just forgot to update the valve pic here and remembered it due to the "1989 screamer" thread.

I do not care the hot idle not being modulated as it does not affect my driving at all. Oil pressure is ok enough (light off), battery is charged even on such low RPM and engine never stalls even if I step on clutch and lift throttle suddenly during driving.

Ie the only pain it causes is that it does not keep 800 RPM. But here for pre 92 or 93 cars the emission spec is pretty easy. Certain emission levels & RPM <= 1000.

Newer cars will be tested idle and high RPM and for diesels box on neutral a engine acceleration from idle to max RPM on full throttle to see how much smog an particles they do.

let me talk about ISC and command authority.HOT engine only ISC only functions hot. (cold is IAC)

this is also about idle duty cycle settings called (TPS calibration)  TPS set right gets the TPS idle switch pin to 0volts DC. (which enables hot  idle controls) 5v turns it off.

the ISC on a hot engine can only change idle speeds with in its range of authority,   (minus 300 to plus + 300 rpm)
this range varies by out door air temps , engine wear or its internal friction. (or its power week or normal)
but when you set duty cycle to 50% (tps cal does that ,using 91 air horn, bleed screw) we set 50%
this make the ISC be in the center of its range,(of authority)

any illegal air leak (vacuum) wrecks this 50% center point,

I have no photo of front of your TB,  ?
like my 91 here. (usa onlyk, in europe changes happen on different years) and also idle up rules not the same as our.

the purpose of this bleed screw is only 2: (1 actually it allows duty cycle setting 10x more easy than 1989/90 USA.
the 89/90 USA are a pain  the TV valve is set for duty cycle but this act can and will cause the TPS calibration to now fail and idle switch opens and kills dead the ISC.
the cure  for that is not simple but is this.
one makes sure the TPS switch stays closed,(idle switch) and adjust the 89./90 TV screw(hot) to get ISC voltages at 50% then last calibrate TPS.
in 91 this is vastly more easy ,we must set TPS first the duty cycle last at the bleed screw below.

in europe some cars (for sure  Santana from spain) has 90 year ECU in 97 year car. wow. tricky.

this is USA spec car 91 and is last 8v sold in USA< banned by EPA after. only 16v after 92 up.(G16)

91+ (engine must be hot, TPS idle pin at 0vdc a must)
no illegal vacuum leaks, (cracked hoses) 
IAC must not leak, after all it is closed fully after 150F and for sure at 180f real hot temp (thermostat not bad for sure not stuck open)

How to set duty cycle more easy?
use an old style (cheap) analog voltmeter, VOM, volt ohm meter. ( most of DMM fail here, do not use DMM unless have 10 kinds to try, no)
set DMM  to 12vdc scale or 15vdc,
put the test leads across the ISC 2 wires, (not easy we use back probing on 91)
TURN the bleed bleed  to meter to 7vdc or 1 half of alternator battery voltage , can be 13.3 volts  or 15 or 14.7.  

this ISC voltage is this. my old scope,
5volts DC is the vertical scale and 200 Hz square wave , it goes with out saying the scope does not lie, DMMs do on square waves
high is 15v ISC is open
0volts is ISC closed
so and analog meter (needle scale) will be 1/2 or 7.5vdc  it averages the voltage, and if wrong turn the bleed until needle lands on 7.5vdc (1/2 battery voltage hot,

the below is not a goal ever, it is not a real hot engine, running, Pulse width modulated. the real goal is 1/2 high and 1/2 low hot.
the ISC moves 200 times a second. in and out. the duty cycle of which sets RPM to 800. (or idle up speed) hot.



step one on all 8v is see of  the bleed screw is there?