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86-95 Trucks & 4Runners 2nd/3rd gen pickups, and 1st/2nd gen 4Runners with IFS

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Old 11-25-2011, 05:31 AM   #1 (permalink)
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A/C on causes RPM drop and engines shakes at idle

What could be the reason? is there an adjustment A/C valve near the throttle body? If so, where is it and how do I adjust it?

Thanks guys
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Old 11-25-2011, 07:00 AM   #2 (permalink)
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do some searches on the forum for IAC. you have to make sure all your components are right, in place and working BEFORE you try to adjust anything. then its a simple adjustment.
BTW: for future reference, try searching the forums first and if you do post a question please give a little more info like WHAT THE HECK YOU'RE WORKING ON........... ;-)
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Old 11-25-2011, 07:11 AM   #3 (permalink)
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It shakes because the rpm's are getting too low. It's supposed to be at 900 on the 22re.

Mine has always done this.
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Old 11-25-2011, 07:46 AM   #4 (permalink)
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Originally Posted by sinful View Post
What could be the reason? is there an adjustment A/C valve near the throttle body? If so, where is it and how do I adjust it?

Thanks guys
See below:
- http://www.4crawler.com/4x4/CheapTri...ne_Pix/13.html
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Old 11-25-2011, 07:50 AM   #5 (permalink)
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if you take the glove box off you can get in there and close to the radio on the lefty side of the glove box there is an idel adjustment nob and you can change it its kinda hard to see but its there
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Old 11-25-2011, 07:54 AM   #6 (permalink)
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if you take the glove box off you can get in there and close to the radio on the lefty side of the glove box there is an idel adjustment nob and you can change it its kinda hard to see but its there
That is the A/C amplifier and that adjustment sets the RPM below which the A/C compressor is cut off. So you want to set that RPM knob to slightly below normal idle RPM. Then when the A/C kicks in, you adjust the knob on the idle-up valve to set the RPM 100-200 RPM higher than normal. Check for clogged vacuum lines, that is the most common issue. Simple test is to plug the inlet line to the VSV to the idle up valve directly and then you can check the idle up valve operation directly (since you have plugged vacuum directly to it).
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Old 11-25-2011, 11:49 AM   #7 (permalink)
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That is the A/C amplifier and that adjustment sets the RPM below which the A/C compressor is cut off. So you want to set that RPM knob to slightly below normal idle RPM. Then when the A/C kicks in, you adjust the knob on the idle-up valve to set the RPM 100-200 RPM higher than normal. Check for clogged vacuum lines, that is the most common issue. Simple test is to plug the inlet line to the VSV to the idle up valve directly and then you can check the idle up valve operation directly (since you have plugged vacuum directly to it).
so for the A/C amplifier adjusment soon as the A/C is turned off, the rpm should drop slight below the normal 900 rpm idle and then immediatly come back up to 900 RPM?

For the idle-up valve (shown in the pic) I should adjust it with the A/C turned on at full blast?

And sorry what's the VSV? vacuum switch valve? is that located before the idle-up valve? so from the VSV it draws vacum from the idle-up valve? to test it, i need to block the vacum going to the idle-up valve?

thanks

Last edited by sinful; 11-25-2011 at 11:51 AM.
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Old 11-25-2011, 11:57 AM   #8 (permalink)
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so for the A/C amplifier adjusment soon as the A/C is turned off, the rpm should drop slight below the normal idle 900 RPM?
FSM has the detailed instructions for setting this (in the AC section). But the basic idea is to adjust the RPM knob so you can switch the A/C on at idle. If set too high, it'll prevent the A/C from kicking in at idle, so keep turning it down until the A/C starts running at idle.

Quote:
For the idle-up valve (shown in the pic) I should adjust it with the A/C turned on at full blast?
Makes no difference full-blast or not, the compressor only runs one speed/load and it just cycles on and off faster or slower as needed. You can adjust it when the A/C is on, or bypass the VSV (see below) and then adjust it any time the engine is running.


Quote:
And sorry what's the VSV? vacuum switch valve? is that located before the idle-up valve? so from the VSV it draws vacum from the idle-up valve?

thanks
Vaccum Switching Valve, bottom center in the image below, idle-up valve in the center, thing with the white hex knob on top. Engine vacuum enters VSV through hose from intake, the A/C amp. sends current to VSV via the wires, VSV opens and passes vacuum to the idle up valve. Idle-up passes filtered air (via the big hose on the side) and sends that into the intake to bump up the idle speed.

Click the image to open in full size.

So basic idea is you have your normal IDLE speed, set the A/C amp RPM to < IDLE and set A/C fast idle > IDLE
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Old 11-25-2011, 11:57 AM
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