So I got my 94 full rebuild 22re. Having issues with power band under load. Ive replaced PVC, wires, plugs, etc etc etc. My buddy mentioned maybe with it being a 230K miles engine maybe the MAF is shot so I pulled the one out of my 91 NO CHANGE, he then mentioned maybe the IAC valve. Idle air control valve in lamens terms. This thing sets under the intake manifold looks like its got some coolant hoses and such running through it. How important is this thing. I looked it up online and its not a cheap part so if you guys know about these things or have one laying around or something let me know cause Im really getting tired of it running like crap when its all brand new (relatively)

ITs been about 20 degrees for the last few weeks, Runs like crap even when cold. No idle surge just power band surge like it goes wide open throttle after a few seconds ALL gears

 

My buddies a mechanic so everything is same name whether different car or not so maybe the air Reed valve is what he's talking about its under the intake manifold has a couple lines going to it he states it controls idle speed when cold but if its stuck the it would kick my truck into some full throttle loop but still surge power band

 

the iac valve cannot cause you to have a power band spike ( or atleast not that ive seen ) even if they stick open its just like having a bigger throttle body, more air in but your MAF and 02 comp for it.

when they stick they usually make it so the truck doesnt idle at all, starts and dies type of situation. If you are having a crazy power band issue i would look into timing, clutch/trans slipping, timing chain jumped, or some crazy wacky stuff from having a lot valves dissconnected...maybe even air leaks from things not being plugged in, but that would cause the idle to be weird and run like poo all the time.

edit: the idle air valve is under the throttle body, it has a coolant line coming into it and out of it. If you take your intake boot off you will see a hole just before the throttle blade, thats the intake for the IAC, if you think its sticking spray some WD40 in there and let it sit for a bit. Put the air boot back on and start her up..

i have seen more MAF flaps sticking then IAC valves sticking, take your MAF off and spray WD40 on the pivots of the flapper thingie and make sure it still springs close, ive seen some where the spring thing goes bad and werid idle/running issues happen

 

If this is the item I think it is ,than yes it can & will cause a problem. As it operates within the coolant temps. And therefore can cause the engine cold start injectors to not operate correctly! Thus a rich or lean situation!Changes the power band!

 

aight I'll try that. I pulled the MAF off my 91 which was running nice but it has been sitting in the cold for a few months so maybe that maf got screwed up too. It makes sense about the IAC. My timing and valves have been gone through 3 times in the last month with NO change and everything has been legit when checking it. It is advanced a bit but so is my 91. This is just irritating. I'll keep working on it.

 

i think mine is prolonging the cold start injector or something.... or at least raising my idle...

 

I heard the IAC valve can be rebuilt is their a writeup on how to do it? Im trying to avoid buying a new one.

 

If I can get it out and clean it, cool with me!

 

I was trying to ask the tech at the dealer that question and he looked at me like I was a fekin moron. Guess they only like NEW parts. Im gonna swap my MAF, air filter, check for vac leaks which Ive done 2x already but hey lets do it again for grins and giggles. If need be maybe pull that valve off and clean it up or just spray the WD40 like someone mentioned earlier

 

I'm not really sure about the problem you're describing, when you say it's "like power band surge like it goes wide open throttle after a few seconds ALL gears" what are you telling it to do at that point. are you holding the throttle wide open and at first nothing happens, then some slightly longer than normal time after flooring it it takes off like WOT or is this normal 10% open throttle going like normal then taking off like WOT on it's own? also, is this auto or stick and is the truck accelerating or just the RPMs spiking?

Yes you need the IACV unless you want the truck to not idle. The valve on these trucks works like a wax pellet coolant thermostat (albeit inversely): heat causes the pellet to melt and expand, closing the valve down for warm idle. when it's cold, it contracts and opens the valve wider. This is why after a coolant drain/fill sometimes the truck will high-idle forever till it works the bubble out of the line going to the IACV.

The idle air control valve does not and cannot alter mixtures under any conditions. fuel is injected according to the MAF/RPM calculation modified by things like coolant temp and fuel trim (O2S). the idle valve is just allowing some air to bypass the throttle plate, no different than opening the throttle.

 

Its 5 speed it opens wide when at about half throttle for a few seconds doesn't matter cold or hot no check engine light I'm going to swap Maf sensor this weekend might look into the injector pulse

 

Truck accelerates I thought it may have been trans or something slipping but its all good in that dept

 

probably not the AFM (MAF) or injector pulse. I'm thinking more TPS. neither the AFM or injectors will make it run BETTER/harder. I'm thinking you have a bad TPS or bad spot on the TPS that's causing it to hesitate when you hit the throttle, then recover and run properly, what you're calling full throttle.

I'm still not positive about what you're describing: so you put it in gear, take off at 1/2 throttle, it's slow for a moment, then fast like WOT and stays that way till you let off or fast like WOT for a moment then goes back to slow/normal? Any way you can get a video? picture=1000 words, video is 30 pictures/second.

The TPS in any car has 2 functions: indicate when the throttle's closed for idle mode (done by a switch in older toyotas like ours) and indicate throttle position. Throttle position isn't really needed as far as calculating injection pulsewidth because it's based on airflow measured by the AFM. What it IS needed for is calculating the airflow before the AFM detects it. 1. our trucks use a mechanical AFM, while small, the door still has inertia and is limited in it's response time. 2. when you snap open the throttle, there is a moment as you're letting air in from the intake duct before the, I guess you could call it vacuum wave, reaches the AFM and actually causes more air to flow through it. the ECU reads from the TPS that the throttle has been snapped open and calculates additional fuel based on amount of opening and how fast, for the moment before the AFM responds. In short, it's used to anticipate airflow. Which is why I think this might be the problem, it's slow right when you hit the gas because you didn't get the extra gulp of fuel, then picks up again when the AFM catches up.

 

Yah I could get video it opens wide ( wot) and stays till I let up on throttle of course this is after the hesitation I will see if I can set it on MPH gauge and talk through it since I don't have a Rachel this might take a few days since I have to replace my intake gasket again cause it started leaking coolant again

 

It is very important. If it is bad or dirty you will have high idle at stop and when you brake at a stop your idle will go up and down. I just found that out after cleaning cleaning the throttle. Whats bad for me is that I did it on both my truck and now both are like that. Got a new one at the auto parts and now it is okay, but still have to use a feeler guage to set it right.