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.



Have you checked for vacuum leaks?Also a good way to see if its the idle air control valve is block off the throttle body opening with something that wont be sucked down the throttle body. If it does die then you have a vacuum leak somewhere.


Saturntech9
May 30, 2012.
A HUGE Thanks for the GREAT suggestion for temporarily blocking the Throttle Body opening! I've done a very cursory check for vacuum leaks (hose condition and connection checking, etc)with nothing apparent at the surface, SO this blocking of the TB will get me more and better info.

HOWever. If possible.I'm still in need of knowing the exact location for the IAC valve on a 1990 Geo Prizm. The part I showed above IS indicated as being an Air Control Valve; however as described earlier, because it has no moving internal parts (that I can tell) I don't believe it is the IAC valve I'm lookin for(?).

Anyone have "hands on" : -) or other direct experience with the 1990 Prizm or even a good engine parts diagram for this prizm

this seems to be such an unusual car for anyone or any reference source to know anything specific about (outside of a dealer setting, which I need to avoid for the moment for financial reasons ). None of the engine parts seem to be in the usual or somewhat expected standardized location. Or it may just be me and my inexperience : -)

Anyways. Thank you (again) Saturntech9 for your super speedy and fantastic response and to all those who have or may be reading this.I DO appreciate your time spent. : -)


Tiny
Amysticalguardian
May 30, 2012.
I need to correct myself if you block off the throttle body and it doesnt die you have a good vacuum leak somewhere. Also you can use carb spray while its idling spray around hoses intake gasket etc if the rpms go up down stumbles or dies there is a vacuum leak present.I need to know what model you have base gsi or lsi?


Saturntech9
May 30, 2012.
A thousand (sincere) thank yous for hanging in here with me saturntech9, (its ABSOLUTELY awesome of you, as a matter of fact : -)

to the best of my knowledge this Geo Prizm is the. BASE. Model.(Exterior trim and door piller is black) VIN Engine Code 6. DOHC 1.6 Liter engine.4AE-FE (?).4 door sedan.



For hoots.I've included a pic of the engine compartment : -) and I WILL reply a couple of more times with just a pic of different angles.{This is like a big scavenger/treasure hunt without clear clues : -D}


Tiny
Amysticalguardian
May 30, 2012.
Here is a pic with a view from the front. But from ABOVE and looking BEHIND the area of the Throttle Body.

(throttle body to the far right of the pic. Engine block/radiator would be toward the bottom of pic)


Tiny
Amysticalguardian
May 30, 2012.
Its supposed to look like the pic I attached I think I see it on the left side of the intake on the end of the intake.


Saturntech9
May 31, 2012.
A view looking from the right(passenger)side of vehicle into the area BEHIND the throttle body assembly.(Intake? Manifold?)


Tiny
Amysticalguardian
May 31, 2012.
And last one.

A closer view looking from the right(passenger)side of vehicle into the area BEHIND the throttle body assembly.(Intake? Manifold?)


Tiny
Amysticalguardian
May 31, 2012.
Can you find the part I posted a pic of?Those are really expensive.


Saturntech9
May 31, 2012.
Yup.I'm fairly certain I'd be able to find the part in a store or online and can you estimate what size this part is? (And you betcha they are quite expensive. Yikes?) However before I'd put out the monies to replace.I'd like to

1. Take a crack at cleaning the interior moving part of that valve.(As I understand can be done) to see if that'll have a positive affect on the high idle. Then. If it doesn't.

2. Do a further deeper check for a vacuum leak. As you've described. Probably do this at the same time and if there is no vacuum leak, the hoses and everything else connected checks out (egr valve. PCV, etc) o.K.

3. Then, as a last resort(?) I'd have to probably replace the whole IAC valve (ugh!). But I've also "heard" that within that IAC valve, there is a smallish motor that is replaceable for waaay cheaper; but I'd have to assess the advantage and overall sense of doing that as opposed to just changing the whole #@%^! Thing : -)

***********
SOOO (yeah!) You said earlier that you think you see the IAC valve on the left hand side (I'm assuming while looking from the front of the vehicle. That would actually be on the passenger side of the intake?)

I know what that part is supposed to look like (and definitely thanks for confirming with YOUR pic) but sadly I still can't see it on my %@#^~ car : -D.(Please refer to the very first pic I attached. The part I'm holding in my hand.

Then look to the forth (4th) pic I posted of a view looking from the right(passenger)side of vehicle into the area BEHIND the throttle body assembly.(Intake? Manifold?). On the left side of the intake manifold you can see that part (I was holding in my hand) with the blue color electrical connector is that what you're thinking you're seeing is the IAC valve?

If it is NOT, then could you please give me a little landmark (such as: go directly across from the oil filler cap OR going from the firewall go to backside of the intake manifold and above, below to the right or left, etc of the rather large diameter vacuum hose, etc etc.I wish we could circle the pic location. Where's john madden and the telestrator when we need it : -D)

ANYWAYS.I've rambled on enough. You are an AMAZING person for dealing with "this" with such patience. Its gotta be hard to have to try and diagnose something "strange" from far away like this.



if for nothing else. We will have been making this "thread" for those who are having the same type of issues with this same #%*&@ vehicle, but either couldn't find the proper location/engine diagram of the part on their own or they're too ("shy"?) To ask the question. : -)

have a Good Night Saturntech9 : -)


Tiny
Amysticalguardian
May 31, 2012.
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