Mechanics

WHAT IS THE LOCATION OF THE IDLE AIR CONTROL (IAC) VALVE

1990 Geo Prizm • 175,000 miles

Having the stereotypical high idle issues usually associated with an IAC valve possibly either going bad or just overly "gunked" up. The engine is a 4A-FE2 (?) Basically a Toyota Corolla engine

I've gone through seemingly every inch of the engine compartment, looked through various web-sites (except this one), part stores and manuals to try and find it; but I cannot seem to find anything that looks like what I believe an IAC valve should look like.

to try and reduce the high idle: I've cleaned the throttle body - as much as I could - I found and cleaned a part that I thought was the IAC valve. It had an electrical connector with a couple of small vaccuum connectors(one that "plugged" into the manifold? On the opposite end away from the throttle body) BUT it had NO visible moving part and no way to get into the housing.(Please see the attached : -)

I also turned the idle adjustment screw pretty much all the way down and adjusted the throttle cable, because it did not appear that the "butterfly" valve of the TB was closing all the way (even after I cleaned all the gunk : -)

and while these procedures helped a bit.I noticed the higher idle was still trying to reassert itself

Sooo. I'm stuck. Apparently I did not locate the IAC valve and would VERY much appreciate your help with location and other ideas


Avatar
Amysticalguardian
May 29, 2012.



It looks like its bolted to the bottom where the throttle body opening is?It looks alot like the pic I posted I can even see a bolt holding it in place. Let me know what you see I could be wrong.


Saturntech9
May 31, 2012.
STAND BY. : -D

{yikes and yuck} I'm bogged down at work so haven't had a chance to check. But I'm thinking you got it located right (and the theory of the IAC SHOULD put it right next to or UNDER the throttle body). Only problem is. Is that it is (might be) under the TB.

For a QUICK look, while I'm here at work; I'll have to get a little mirror to squeeze through the openings and look under the TB without removing anything that is currently in the way.

I'll DEFINITELY keep you posted. We're in this together saturntech9 : -)


Tiny
Amysticalguardian
May 31, 2012.
I really belive from that pic it sure looks like its bolted under the throttle body opening. Keep me posted and yes were in this one together good or bad lol.


Saturntech9
May 31, 2012.
: -)

BINGO! That's it!

With a broken piece of mirror I was able to confirm that you nailed the location! [Woo hoo!]

(O' don't worry, I broke the mirror on purpose which invalidates the curse. Has to be broken by a careless accident to get the 7 years of bad luck: at least, I hope so. : -D)

Anyways : -). From the photo YOU provided of the part; it is mounted upside down on the bottom of the throttle body.(It'd be nice if car manufacturers didn't have to put stuff in such an inaccessible place. EGADS. That's gonna be a pain to dismount : -D]

now the last and only question to figure out is: there is NO visible sign of an electrical connector ANYWHERE on the valve housing as I imagined would then go to the idle air control motor (as I've attached a parts picture below).

Could it be that such a motor is internal. Within that IAC Valve (once it is removed from the bottom of the TB)?

OR

does the guts of that valve. Does this vehicle even have or need such a motor?

Is it just a simple mechanical. Air/vacuum propelled. Component that moves as the air is passively drawn in or out, etc etc?

OR

is the IAC motor (as picture below) somewhere else on the intake manifold? (I would kind of think not, since it should all be working together in close proximity. Attached?).I'm going out to look at one LAST spot on the intake manifold. We're really SUPER close to the end of the original intent/need of the question.

I'll keep you informed. Prolly tomorrow-ish. : -D

YOU DID AWESOME! (Or as the kids say today.) YOU ROCK! : -D
this is kind of a Fun little treasure hunt and I get to get dirty. So yippee : -)

Have a GREAT evening saturntech9. Chat with ya later. : -)


Tiny
Amysticalguardian
Jun 1, 2012.
Didnt forget about you I have just been busy working on cars.I know what you talking about I have never seen a idle control solenoid like that which without a connector it really isnt a solenoid. Must be vacuum controled thats all I can figure I will do some reading on it when it get time later.


Saturntech9
Jun 1, 2012.
Whaaaat? You mean I’m NOT the only one in your life that your spending time on? WELLLLLL! Of all the nerve! : -D (and here I thought I was special and not just because I rode in a short yellow bus) : -D

I appreciate the “check in” from you…. But I never lost faith that you ’d be back here whenever you could…I kind of figured {hoped : -D} you had a life outside of just staring at your computer monitor reading my rambling messages : - )

Speaking of rambling: here's more.

The truly annoying thing about this vehicle is that it is almost like the designers were experimenting with the newer computerized technology that was JUST starting to be imagined (and would-sadly-become a standardized design for the later years) while still keeping some of the old mechanical elements intact…and they seemed to have mixed and MASHED both type of components all together into this vehicle and probably other ones too, during this early 90’s era….(Some parts in this car just don’t make sense as to why they’re here when coupled with basically electronic/computerized components, too)

But anywhooo…I’ve come across a couple of things as I’ve been surfing the web; trying to come up with some answers for US : -D

1) I found a more close up pic of the underside of THAT part YOU found for me and as I zoomed in I could see something of a spring /screw type “drive” system inside AND I came across a youtube vid of some other vehicle (totally different make model, etc think it was like a Silverado Pick up or Jeep or the like) and the type of IAC they were showing was similar…with no electrical connection.

But in order to repair it the person in the vid…had to remove the brass end cap…and inside was a flattened plastic looking disc with a couple of slots cut across it and by placing a flat head screw driver in one of the slots he rotated the disc till it was wound back downward again…essentially he seemed to be resetting the? To its most effective (or original) level…. Don’t Know IF this is what WE got inside of our valve or it’s something else entirely….

AND

2)I also found (by accident) a geo metro forum which seemed to show in one of its threads, an IAC valve, that looks amazingly like the VERY first pic I posted above in this long thread and their thread went on to describe how they gently pulled back some of the SMALL metal hasps that were surrounding the top…and removed the top housing where those hose connectors were and revealed a type of piston inside {see the pics I attached below with this one)

Sooo I’ll do a little bit of “on car’ investigation this weekend to re-look at that component I posted a pic of first above (but prolly not much else in regards to removing the TB and getting a good clear visual on OUR IAC valve, cuz I won’t have access to getting a TB replacement gasket should I find I need one after my gorilla attempts to remove the TB…just to be on the safe side) AND, of course I’ll definitely keep thinking about this, looking and reading also….

Since you've got waay more experience, expertise AND resources I'll definitely look forward to what you've been able to discover. BUT. BUT. Please know only as you're life allows and at your convenience. This isn't a "hair on fire type of emergency", its turned more into an annoying, but fun(?) Type of obsessive challenge.

HAVE A FANTABULOUS WEEKEND Saturntech9. Rest well (when ya can) and play often.

Chat with ya later and thanks again for ALL of your thoughts and efforts.

[the following pics are from that Geo metro forum for comparison]


Tiny
Amysticalguardian
Jun 2, 2012.
2)


Tiny
Amysticalguardian
Jun 2, 2012.
I do belive I have solved are mystery my friend I looked up the 1990 toyota corolla which should be the same engine.I posted my findings bellow the one on the throttle body should have a coolant feed going to it. That is the aux air valve that gives the engine extra air when the engine is cold. It uses the coolant feed to determine when the engine is cold. Must have a thermostat inside it. The one on the end of the intake is the idle speed control aka idle control valve read the descriptions I posted bellow sounds like there talking about the two valves we were talking about. Were getting there lol.


Saturntech9
Jun 2, 2012.
Well Shoot Howdy, I’ll be dipped in sugar and fed on by ants: -D

That’s absolutely PERFECT! ….I’d have to say we ARE there…. : -D

You Were a bit busy reading this weekend, Uh? VERY Nice! (Very, VERY much appreciated, too : - )

in combination with what I was able to discover this weekend…it looks like we’ve got this pretty much corralled and almost branded… : -D ….I love it when the pieces of a puzzle start coming together and the truest picture is revealed…. : - )

I’m fairly certain now…after reading the descriptions you posted…that the “Auxiliary Air Valve” (which is located UNDER the throttle body) is NOT the culprit to the high idle issues…. It does NOT seem as if it could really fail in this manner. Just by its very function, it seems like it has got a fairly limited and straight forward function (essentially just reading the temperature of the coolant – with no real moving parts or regulatory function; per se)

SOOOOOO…. As I mentioned in my previous post on Friday…even though I was only able to spend a few moments under the hood this weekend and I was able to confirm that, apparently, this “mystery part” I alluded to on Friday (and in my VERY first picture post above) is exactly what we were looking at from that “metro forum; ” YOUR post on Saturday from the Mitchells site (which I was just able to see this afternoon)…OFFICIALLY verified (THANKS TO YOU!) That this “mystery part” is no longer a mystery; but is in fact a vacuum switching valve OR Idle Speed Control…located on the far end away from the throttle body… and is akin to the type of idle air control “motor”-like part we were searching for….[Essentially mystery solved. BIG sigh of relief]

Now that a “suspect” has been identified; the kind of fun part begins: gotta find a new replacement part to be on the “safe side” …(I’ll do other testing to make sure the integrity of the vacuum system, hoses etc as well as the electrical connection is still sound…but from what I can see and hear already I’m sure this part is the ONLY culprit…besides it’s over 20 years, even IF I do find something else contributing to the high idle…which I now seriously doubt will happen…thanks again to your posting of the “mechanical theory”. It should be replaced anyways : - )

I’ve already tried to “surf” the internet…looking for THAT part (besides my getting swamped at work that’s another reason why I’m late in replying here)…but so far I have had no joy. When I put in the phrasing : 1990 corolla or Geo prizm along with any combination of terms: Idle Vacuum switching Valve or just plain Vacuum switching valve or Idle Speed Valve…none of the parts that “Come up” under those headings look EXACTLY like the one I’ve got currently on my car…So I wonder will I have to somehow utilize a modified. Re-configured part? (Yikes I may have to go to the dealer parts dept : -O …. But even “They” might not have access to that exact part anymore?)….

So Any thoughts or ideas you might have on the right terminology and/or a link to where I could find the part…would put a nice little bow on this package…and of course : - )

Even IF we had not been able to fully identify the location of the part…you still would’ve done AN EXTRAORDINARILLY WONDERFUL JOB! SOOOO WONDERFUL, by the way; that I’ve already started court proceedings to have one of my kids RE-NAMED: Saturntech9…. In honor of you and your never failing efforts to stay at my side and help solve this “mystery” ….(Of course within the house we’ll just call him “Satch9” for short, but out in public and in school…he’ll proudly be known as……Saturntech9…)

: -D

Sleep Well Saturntech9…Have a Tremendously Terrific Tuesday and I’ll look forward to keeping you updated and chatting with you again real soon. Be good TO yourself as you are clearly doing for others. You deserve it. : -)


Tiny
Amysticalguardian
Jun 5, 2012.
As far as the correct terminology of the parts name I would use the name given in mitchell ondemand.I have been doing some searching myself for the part but have had no luck. If we could get the part number that would really help. You should call the dealer and see what they have to say maybe even get a part number.


Saturntech9
Jun 5, 2012.
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