Thinking Outside of the Box: The IACV You Need In Your Life!

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Turtle
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Thinking Outside of the Box: The IACV You Need In Your Life!

Postby Turtle » Fri Apr 19, 2013 5:38 pm

Thinking Outside of the Box: The IACV You Need In Your Life! Presented in HD with no commercial interruptions.


Once upon a time in a magical land called The Bay Area, Turtle was about to tackle a problem that many Corolla owners have had to deal with.


Turtle and Shelly were stopped at a light when Lola started acting hella weird.


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The Idle started surging.


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How annoying, the surging won’t stop!

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What’s worse, that dude in the Viper next to them thinks that they’re trying to race him. How embarrassing!



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Turtle pulled over and tried to diagnose the situation. Maybe the Idle screw needs adjusting…


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No dice. The Idle screw is all the way down and yet the idle still surges.



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Let’s speak about the Idle screw for a moment. On the throttle body, there is a passageway for air to enter before the throttle body and exit after the throttle body, a bypass, if you will. In order to control this air, there is a screw somewhere in the middle that acts as a valve. When the screw is all the way up, the airway is completely open. When the screw is all the way down, the airway is completely closed.



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If the screw is all the way down and the idle still surges, then where the eff is the extra air coming from that makes the idle surge so much???


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Well here’s your answer: It is most likely the IACV, or Idle Air Control Valve (I say most likely because it could also be a vacuum leak).



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It, like the Idle screw is a passageway for air to get past the closed throttle body. On the 4ag engine, it is located underneath the throttle body. This is how it works: The IACV is connected to coolant lines. When the engine and the IACV are cold, the valve is open. When the valve is open, air can enter the engine by bypassing the closed throttle body. As the engine warms up, the warming coolant going through the IACV causes it to close. When the engine is at operating temperature, the valve completely closes, thus blocking off the air that is no longer needed for the engine. The IACV is essentially needed for cold starts and without the air that the IACV provides, the engine has difficulty getting and staying started. It’s certainly not impossible to start, but the open IACV is designed to help with cold start-ups.



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So if the IACV is stuck open and it does not close when the engine warms up, then very often the engine will start surging, also known as hunting, which may mean that the engine (rather, the ECU) “hunts” for the correct mixture of air to fuel. (someone correct if that's wrong) Others have experienced unusually high idle with no way to bring it down to an acceptable level.

What are some possible problems and solutions to a hunting idle and one suspects that it’s the IACV?

First, check if the IACV is still operational. Remove the IACV and submerge it into some hot water (as hot as normal engine operating temperature). If the valve moves, then it is very likely still working. (read about it here: viewtopic.php?f=9&t=2569&p=14400&hilit=iacv) One may be able to pinpoint the culprit either being an obstruction of the coolant lines or air pockets that need to be bled out. One also should not rule out a vacuum leak. Find the obstruction or burp the lines, and if the problem is solved, move along with your life.

Second, if it is determined that the IACV is no longer operational, then one can replace it with one that does work.

If one is not in a position to replace the IACV with a working one, such as being unwilling to pay more than they think they should for a new one or one that works, then there is another option than many have relied on: They remove the IACV completely and block it off with a plate. Here is one of those block-off solutions, which Turtle had actually bought.

http://www.ksdengineering.com/KSDEngine ... _p_19.html

As Turtle was about to install the block-off plate, he thought about how difficult it might become to start Lola on cold mornings. He just didn’t want to hear the crank-cough-stall, crank-cough-start that he might experience. Poor Lola. There must be another way. He wondered if it might be a good idea to drill and tap a hole into the plate that he could manually block off when Lola was warm. What to do?

That’s when Turtle wanted to know where the air for the IACV was coming from. He determined that the air enters before the throttle body through the smaller hole in the middle and that it exits behind the throttle body through the larger, strangely shaped hole on the right. Coolant enters the IACV through the hole on the left and exits through the throttle body, not part of the IACV.


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He noticed some vacuum tubes on the IACV that appeared to be for other things. Turtle attached a vacuum hose to one of these tubes, stuck it in Shelly’s mouth and told her to blow hard. Enough to take the chrome off a trailer hitch.



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Well fascinating! It would appear that the vacuum tubes lead to the larger oddly shaped hole behind the throttle body! Turtle had an idea!



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Here is a for reals picture of it:



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Turtle believed that if he were to close off the air opening for the IACV, it would work JUST like a block-off plate. Furthermore, if he were to add a vacuum line to the IACV’s vacuum tube and add the other end to an inlet BEFORE the throttle body (and block off all other vacuum tubes), it would act JUST like an open IACV! From there, there are many options to close that tube off when the engine doesn’t need that extra bit of air.



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Here is how Turtle decided to block off the IACV air opening:

He blocked it off with Permatex Blue. He filled the hole all the way and allowed it to cure overnight.



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After re-installing the IACV, it did, indeed act like it was blocked off. Turtle then added a vacuum tube leading from the IACV to the vacuum inlet found on the air hose in between the throttle body and the air box, which may have been reserved for A/C (Lola is not equipped with A/C).

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Since the IACV will no longer operate on coolant, Turtle looped the coolant lines from the engine block together. A redundancy, sure, but perhaps it would serve as a good entry for a water temp sensor (but that would be for another day)

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The IACV no longer needs coolant, so either leave the coolant lines capped or uncapped. It’s just a matter of preference, it doesn’t matter.

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Turtle blocked off all possible areas for vacuum leaks, namely the extra vacuum tubes. One would be wise to check these from time to time as rubber plugs can get old and create leaks.

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And finally, Turtle devised a way to open and close this passageway.

The rough idea at inception was to have the vacuum tube lead into the cabin so that Turtle could pinch it off with some forceps. Crude and perhaps inefficient, yes, but Turtle thought there might be a better way. Maybe a shut-off valve from the Home Depot or something. Turtle rummaged through his spare parts and found something better.

He had a spare A/C idle up solenoid lying around and wondered how it worked. It must do exactly what its name implies. Did it do something fancy like blow extra air into the tube with an internal fan? No. It is simply a magnetic valve that opens and closes, depending if it’s powered up or not. Incidentally, the opening is the same size as that of the IACV’s opening. It also has an adjustment screw. That’s it, and that’s exactly what turtle needed. He added the A/C idle up solenoid to the new vacuum line (in between the IACV and the air hose) and wired it up for 12v power with a switch.

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So here is how it works. Instead of taking air in before the throttle body through the IACV and exiting behind the throttle body through the IACV, the air comes in before the throttle body through air hose vacuum line, passes through the A/C idle up solenoid (just a valve that opens and closes) and exits behind the throttle body through the IACV. It is no longer an automatic mechanical valve. It is a manual valve that Turtle can open or close with the flip of a switch!




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What’s that now? A bunch of mumbo jumbo, you say? Too far fetched to be true, you say? Too complicated, you say? Well here’s the result:

https://www.youtube.com/watch?v=yC5liOa3aEE

It honkin' works! Fare thee well, hunting idle. Don't let the door hit your @ss on the way out!

Peace in your hood,


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R
Last edited by Turtle on Mon Apr 22, 2013 12:00 am, edited 5 times in total.

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kuvyoghmoob
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Re: Thinking Outside of the Box: The IACV You Need In Your L

Postby kuvyoghmoob » Fri Apr 19, 2013 11:24 pm

Wow sweet write up... Thanks man. I'm going to try this tomorrow. ;)

masagsxr
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Re: Thinking Outside of the Box: The IACV You Need In Your L

Postby masagsxr » Sun Apr 21, 2013 12:41 pm

+1... Great addition

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Re: Thinking Outside of the Box: The IACV You Need In Your L

Postby Deuce Cam » Sun Apr 21, 2013 4:41 pm

Holy crap this is amazing. It sounds like you basically converted the thermo iacv to a custom manual air controlled iscv. Well done sir!

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Re: Thinking Outside of the Box: The IACV You Need In Your L

Postby chocobot » Thu Apr 25, 2013 11:47 am

Ladies and gentlemen, this has been another quality write-up by the one and only, Professor Turtle.
-gasp- "..oh!, how does he conjure up such mechanical contrivances?!"
Your skill in reading has increased by one point.

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Re: Thinking Outside of the Box: The IACV You Need In Your L

Postby chocobot » Thu Apr 25, 2013 12:05 pm

Turtle wrote:..the rough idea at inception was to have the vacuum tube lead into the cabin so that Turtle could pinch it off with some forceps. Crude and perhaps inefficient, yes..

Entertaining, double yes
Blow a couple breaths of air into a tube while starting Lola.
Halfway to your destination, you ask your passenger to pinch the tube off with a pair of forceps.
I could already see the question mark floating above their head
Your skill in reading has increased by one point.

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Re: Thinking Outside of the Box: The IACV You Need In Your L

Postby kunfuzion » Thu Apr 25, 2013 4:45 pm

Wow, nice discovery. Now I can find a use for the useless AC idle up that I had laying around, well at least when the IACV fails.

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Re: Thinking Outside of the Box: The IACV You Need In Your L

Postby yoshimitsuspeed » Sun Apr 28, 2013 3:56 pm

Why not just fix or replace your IACV?
Seems like a ton of work to add more crap to your engine bay to do a job the motor used to do automatically.

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Re: Thinking Outside of the Box: The IACV You Need In Your L

Postby mikeyee » Sun Apr 28, 2013 10:10 pm

A+++

Something I'll probably try out myself! Good stuff Ron!

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Turtle
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Re: Thinking Outside of the Box: The IACV You Need In Your L

Postby Turtle » Mon Apr 29, 2013 8:09 am

by yoshimitsuspeed » Sun Apr 28, 2013 3:56 pm

Why not just fix or replace your IACV?
Seems like a ton of work to add more crap to your engine bay to do a job the motor used to do automatically.


What are some possible problems and solutions to a hunting idle and one suspects that it’s the IACV?

... First, check if the IACV is still operational...

... if it is determined that the IACV is no longer operational, then one can replace it with one that does work.

...If one is not in a position to replace the IACV with a working one, such as being unwilling to pay more than they think they should for a new one or one that works...


R

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Re: Thinking Outside of the Box: The IACV You Need In Your L

Postby taroroot » Thu Jun 27, 2013 9:17 pm

I'll have to remember this. As for adding more crap to engine bay, you're not adding any more crap in engine bay that there wasn't before, you're just repurposing the A/C idle up! Hey, the 20V does idle up in a similar manner with an electronic controlled air valve instead of the wax valve with radiator fluid hoses running to it to get crudded up, air bubbles stuck in it, AND expensive to replace with a factory new one if you decided to.

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Re: Thinking Outside of the Box: The IACV You Need In Your L

Postby KonaTrueno723 » Wed Jul 03, 2013 12:27 pm

Great write up turtle,, thanks.
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