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what is the idle up valve?

33986 Views 15 Replies 3 Participants Last post by  sb5walker
can anybody tell me what the idle up valve on the intake is for and how to set it on the 22r-e in a 93 pickup?:confused:
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It's called the "auxiliary air valve" in the manual and it's part of the throttle body, located below the throttle valve (butterfly). It's a thermostat-like coolant-operated device that allows extra air to bypass the throttle when the motor's cold. It is sometimes called the "cold idle air bypass". When the hot coolant hits it, the valve is supposed to close the air passage, reducing idle speed.

The main air bypass - that controls the hot idle - is above the throttle plate, and is controlled by the idle set screw - the large screw on the top of the throttle body. It allows air to bypass the throttle plate at all times. It is sometimes referred to as the "hot idle air bypass".

There is no "setting" on the aav: it is supposed to be open when the motor is cold, and closed when the motor is hot. It can get gummed up and get stuck open or closed, and also the thermostatic device can fail, though it normally lasts very many years and miles. If coolant is low, that can also cause the aav to fail to operate.

I think on the 22re the aav can be removed and replaced with one from a junkyard part, but I don't think you can buy the aav by itself from the dealer. On the 3vze, the aav is an integral part of the throttle body and so if it's bad, the whole throttle body must be replaced.

There is a simple test to see if it's working. When the motor is cold, start it, and immediately screw the idle set screw all the way in (count the turns). If the aav is open and unclogged, as it should be, the idle speed will go down but the motor should still run. Back out the idle screw to it's original position and wait for the motor to get hot. Then turn the screw all the way in again. The motor should stall, or nearly stall. If the motor doesn't stall, or if there isn't a difference in idle speed with the screw all the way in hot vs. cold, then the aav is not working.

If the problem is that the aav is clogged with gunk, you can often get it working again by cleaning it. Get some O2 sensor- and catalyst- safe throttle body cleaner, a clean rag and toothbrush, and clean the throttle body, giving several good shots into the holes in front of the throttle plate, above and below. Those are your air bypasses. Clean the back of the throttle plate with the toothbrush. Be very careful not to get any of the cleaner on the black plastic throttle position sensor, as solvents will kill it.

Once the throttle body is clean, set the hot idle speed to 750 rpm (22re) or 800 rpm (3vze) with the idle set screw.

There's one additional air bypass, and that's the A/C idle up VSV (vacuum solenoid valve). It provides an additional air bypass when the A/C compressor is compressing.

It's a two part device: the a/c vsv, and the actuator. On the 22re the vsv is on top of the valve cover and the actuator is attached to the engine side of the plenum between the "E" and the "F". It has a big hex-shaped plastic screw which is used to set the amount of a/c idle increase. (On the 3vze they're both on the passenger inner fender.) The way the thing works is that the vsv applies vacuum to the actuator when the a/c compressor is on, which causes the actuator to open and allow additional air to enter the plenum, increasing the idle speed.
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its not on the throttle body its on the side of the intake ill take a pic and post it in a min.
That's the A/C idle up actuator - is that what you mean? It's attached to the engine side of the plenum between the "E" and the "F", and has a big hex-shaped plastic screw to set the idle speed increase when the a/c compressor is operating - I mentioned it at the end of my first post.
i cant figure out how to ad a pic.
i think what you last described for the a/c idle up actuator is what i am talking about, how do you set it?
When the motor is hot, turn on the a/c - the idle speed should go up. Turn the a/c actuator screw in or out to lower or raise the a/c idle speed. If the idle speed doesn't change when the a/c compressor is engaged, check the a/c vsv - instructions in the factory manual in the AIR CONDITIONING - VACUUM SWITCHING VALVE (VSV) section. If you don't have one, google 1993 toyota pickup service manual.
Would the cold idle valve make my truck run bad for the first 30 seconds or so after a hot start? Every time I start the truck after its warmed up, it idles really low and runs like crap below 2000 rpm.

It starts and runs great when started cold...
Would the cold idle valve make my truck run bad for the first 30 seconds or so after a hot start? Every time I start the truck after its warmed up, it idles really low and runs like crap below 2000 rpm.

It starts and runs great when started cold...
No, the aux air valve should only change idle speed, but it should run fine when the motor is hot no matter whether the aav was open, closed, clogged, not working or whatever. So I think your problem must be something else.

I would check IDL-E2 in the TPS for continuity when throttle is closed (idle position), and I'd check the ECT, and clean the throttle body, and check the VAFM, and I'd check for leaks in the air hose between the vafm & throttle body. If nothing, check for vacuum leaks, check the signal rotor clearances & signal coil resistances in the distrib, clean the injectors with red line si-1 complete fuel system cleaner, make sure plugs, wires, cap & rotor & air filter are in good shape, check cat for clogs...

You know, like that.
All new plugs/wires/cap/rotor/filters. If the AC is on, it doesn't do it. If the AC is off, it clears up after 20-30 seconds and runs like a sewing machine.
Well now you didn't say it only does it with the A/C off :hammer:

And the motor you have is? And the transmission?

Do you have the 22re?? If so, your throttle body probably needs a good cleaning. It's best to remove it, though you'll need a new gasket. Use a 3M or Wurth throttle body cleaner and be sure to thoroughly clean the upper and lower air bypasses. On the 22re I think you can remove the aav to clean and inspect. Be very careful not to get any solvent on the tps - that will kill it.

If you use a cleaner other than 3M or Wurth, then finish by putting just a drop of light machine oil (like 3-in-one) on each end of the throttle plate shaft and work it in, wiping the excess with a clean rag.

Reinstall with 14 ft-lbs (22re) or 13 ft-lbs (3vze)

If you have the veezy it's not as likely to be the throttle body, but, wouldn't hurt to clean it anyway.
Sorry- I posted a thread on this issue a while back and didnt get any responses.

94 22RE, 5spd 153,000 miles. I have done the following:

cleaned TB
cleaned the air valve on the bottom of the TB
adjusted the valves
replaced all maintenance items (except o2 sensor- toyota refused to replace it under warranty as per the owner's manual)
timing chain kit
oil pump
water pump

No DTCs stored in the computer and the truck runs fine except for the first 20-30 seconds after a hot start. It idles at about 500 rpm and stumbles when you press the accelerator until it reaches 2000 rpm and then it revs fine. If the AC is on, the increased idle speed seems to remedy the problem.
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I'm curious about the idea of the O2 sensor being under warranty? What warranty would be in effect on a 15 year old, 153,000 mile truck?

At any rate, if the O2 sensor has over 90k miles, if definitely needs replacing - that could be your problem right there. has excellent prices, and if you get the denso part # from sparkplugs, you can search for it on amazon. I got a denso sensor for my 3vze from the PartsFactor vendor on Amazon last week for $62.40 shipped - ordered it at 11 am Thursday and Fedex Ground handed it to me at 10 am on Friday. I think the 22re sensors are more $$, for some reason. If money is tight, you can try your luck with an NGK, but avoid the Bosch.

You might check your cold start injector time switch. Perhaps it's firing the cold start injector when the motor is hot, which it shouldn't be doing.

If it's not the sensor or time switch, you might try running through the list in post 10.

Good luck.
I'm curious about the idea of the O2 sensor being under warranty? What warranty would be in effect on a 15 year old, 153,000 mile truck?
Page 31 or so of the owner's manual states that once the truck reaches 80,000 miles, Toyota will replace it for free. Long story short- Toyota will only replace it if you bring it in at EXACTLY 80,000 miles (this is not stated anywhere in the manual). They had this in the OM to comply with one of the clean air laws in the 90s. I didn't really expect them to replace it, but I thought it was odd that none of their stipulations were in the OM.

I will replace the o2 sensor and check the cold start switch- where is it and how do I test it? Given the very specific nature of the problem I suspect that may just be the issue.
The time switch is below and to the right of the throttle body, next to the engine coolant temp sensor (which you probably ought to also check). You'll need an ohmmeter. See this post for more info:
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