HelliphinoN8

It's an idle, air, control valve. I just need to know what it looks like and where it's located. I think this may be causing my idle surging.

keithdphan

iac valve is located directly under and attached to the throttlebody. it has coolant hoses connected to it.

91Toyota

HelliphinoN8

Awesome, Thx guys!. Has anyone heard that this going out could be one of the things that could cause idle surging?

91Toyota

Yep. Is your idle screw turned all the way in? You can also put a piece of tape (duct tape) over the holes in the throttle body and it will act a little funny but it won't or shouldn't surge.

keithdphan

they normally get clogged

thook

The real way to test the IAC valve is when it's cold and hot.

In case you didn't know, it's an auxiliary/supplementary air valve that is suppose to remain open until coolant warms to operating temp thereby allowing extra air past the closed throttle plate in order the speed up the idle. As the coolant heats, and since the valve is thermo regulated, it's supposed to close slowing the idle down. So, if you understand that, you test by adjusting idle speed bypass screw all the way in shutting off the only other source for idle air.

Begin by starting the motor cold. Turning the idle screw in should only drop the idle down to around 100rpm. At this point, the open IAC is the only source for air. Turn the screw back out and let the engine warm. (At this point, the idle speed should've dropped to the 750 idle speed, anyway.) But, if not, turn the idle screw in and the idle should drop below 100rpm. If there's no difference from the cold fast idle, likely the valve is stuck open. This is what can cause surging....too much air to fuel ratio. Fuel is supposed to lean out when the coolant temp sensor resistance drops from rising coolant heat. (Which, btw, can also cause surging....a bad sensor, that is)

If, on the other hand, the valve is stuck closed (usually the case) or the air passage is just clogged, you will have no cold fast idle and the truck will barely run.

If you do have a cold fast idle, the IAC or auxiliary air valve (as Toyota calls it on early models) is not your problem and testing the valve is pointless.

thook

BTW, they don't normally "get clogged", actually. It's a relatively large air passage. What happens....particularly with the way your throttle body is designed...is the crankcase gases being sucked in by the breather line cause the valve to stick.

ssupercoolss

my truck had a great high idle when cold, then after it warmed up, it would start to surge up and down. it was the aux air valve that was my problem. mine was plugged with an rtv bugger in the coolant line heading to the valve. no coolant flow=no valve worky.

thook

I meant "normal" cold fast idle....wherein it slows down to a "normal" idle.

I knew I should've elaborated on that last statement, but I got tired of typing and hoped I'd explained it well enough in the third paragraph (sticking open = surging once warm) that whom ever would see what was going on and figure it out while testing.

Regardless of that, I hadn't thought of the coolant line plugging. I was only thinking of terms of the air passage itself.

pcmentor

I have a concern the o-ring in the air valve is or isn't supposed to pass air. It seems strange to design it to pass air but when the valve heats up it doesn't pass air through the plate but only through the o ring. So any ideas are welcome. Thanks

thook

Oh....I see. I posted in the other thread wondering what seal you're referring to.

I don't recall the o-ring when I'd had mine apart. Can you take a pic? Otherwise, I'd have to pull mine off again (and it was sooo much fun) to know what you're talking about.

At this point, all I can tell you is the valve/plate is supposed to pass air through the large eliptical hole when cold, and then shut when it's warm. So, it appears that function is operational.

Maybe you could describe where the seal is within the valve?

Edit: So I'm sure we're on the same page, does yours look like this? It should.

pcmentor

My valve looks like the pic. With an electrical connector in back. The reason I say it's supposed to pass air when hot is in the FSM page FI-58 I believe it says when hot pinch hose and rpm should drop less than 50rpm's. Thanks

thook

That's because you still have air passing through the idle bypass, and at that point the motor has warmed up and the ECU has adjusted accordingly. The valve plate does have very small holes, but the plate is supposed to shut closing the large hole nonetheless.

toyotc78

if you are low on coolant or you have air in the cooling system it will cause your 22r to idle up and down. check your coolant level and heater operation. vacuum leaks can also cause those engines to idle up and down

pcmentor

Thanks, I thought the small holes in the plate were supposed to pass air when hot but when I heated it up on the bench no matter how I adjusted the plate, when hot the small holes weren't in the right place to pass air. Have you played around with it and gotten the small hole to pass air when the bimetal is pushing the plate closed when hot? Idle bypass won't be affected by pinching the air valve hose will it?Thanks for your support.

pcmentor

I think the coolant hoses are on the air valve to keep it hot say when you turn off the engine at a store and then come out 20 mins later. The valve will still be hot without having to heat up the electric bimetal lever electrically. How does this sound?

thook

Hi....again.

I posted in the other relevant thread my thoughts. I do believe we're on the right track. Sounds 'bout right, to me.

But, hey....listen....I'm still trying to wrap my head around this whole thing. Just found out that the heated element power is supplied by the circuit opening relay switch (my COR is bypassed because of corrosion, and I'm not sure how it's affecting my situation). So, would you do me a favor and read this?
http://www.autoshop101.com/
Together with your FSM source and what I've offered, we should be able to clear this up.....for your vehicle and mine.

thook

Okay. Apparently you're right. The AAV should pass a minute amount of air when hot. When the hose is pinched while the motor is warm, the idle drop should be less than 50rpm. So, if you're idling at 750rpm, it should drop to around 700 or so.

I'd confused info for the wax type air valve with how the bimetal type operates. The wax type fully closes when hot.

pcmentor

I am going to put the rubber o-ring back in the air valve. I have a vacuum leak that's leaning out the mixture(per O2 Sensor reading). Hopefully with the air valve passing no air when hot the vacuum leak problem will go away.