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Discussion Starter #1 (Edited)
I gather that if you want to convert from OBD2 to OBD1, you need to change the IACV from 3 pin to 2 pin in addition to some wiring modifications. the reason for this was supposed to be tht the 3 pin IACV is driven off a PWM signal while the 2 pin IACV is operated by a simple voltage differential signal.

being the cheap and lazy bastard that I am, I wanted to see for myself whether or not a 3 pin IACV could be run by a voltage differential signal. I had one lying around so I took that, an AC - DC adapter with a variable output voltage setting, couple of wires, alligator clips and went to work. here is the result [annotations added]:


with this, I am pretty certain that a 3 pin IACV can be run by an OBD1 ECU. all that needs to be done is to use the center terminal and one of the two outermost terminals. the center pin takes a constant positive voltage and the outer pins take varying amounts of negative voltage and the difference between the two voltages determines how far the IACV opens. which one of the two outer pins the voltage is applied to determines the direction in which the shaft rotates. with an OBD2 ECU, it can rotate both ways. with an OBD1 2 pin ECU, it will rotate only one way. my guess is that the ECU should be able to learn to control this valve. will know for sure when I get around to doing my conversion.

@2jzdreamin, @xile6, this should be of particular interest to you guys.
 

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Discussion Starter #3
2 pin IACVs are sorta rare to come by here and expensive. they also require intake manifold modification.

this method requires no modification other than wiring. almost plug and play shit.
 

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Discussion Starter #5
true. but still something I would still like to avoid as this alternative is way simpler. Im getting a 2 pin IACV as a backup though. it the ECU cannot control this, Ill go the conventional way.
 

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can you describe what happens? and what did you do for the wiring? get rid of the orange IACVN wire and retain the blue / black IACVP?

It has been a while ago, but IIRC if had a very limited range of idle control.

Yes, that is how I set it up IIRC.
 

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Discussion Starter #9
thanks dude. gotta ask you one more thing... did you try adjusting the plate on the other side of the IACV to give it some range?

here is what I found it could do:

regular setting:


tweaked setting:
 

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being the cheap and lazy bastard that I am, I wanted to see for myself whether or not a 3 pin IACV could be run by a voltage differential signal. I had one lying around so I took that, an AC - DC adapter with a variable output voltage setting, couple of wires, alligator clips and went to work.
I've always found it slightly entertaining to see lazy people work twice as hard while attempting not to do any work at all. Carry on and good luck :biggrin:
 

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Discussion Starter #12
I've always found it slightly entertaining to see lazy people work twice as hard while attempting not to do any work at all. Carry on and good luck :biggrin:
LOL! thanks man.

it is like an investment. if a little bit of work today helps me be lazy tomorrow, I go for it :D
 

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yes it does...

please search the forum before jacking someone's thread, i am sure there's more than enough info on the forum
 

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Just wondering, it's easier to just cut one of the wires and splice them together for the iacv? then just plug it, it seems like this is a lot more work.
 

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Discussion Starter #18
Just wondering, it's easier to just cut one of the wires and splice them together for the iacv? then just plug it, it seems like this is a lot more work.
it is easier if you already have a 2 pin IACV. I am simply interested in checking if it is truly impossible to make an OBD2 IACV work with an OBD1 ECU.
 

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2 - Wire is for Manual trans ecu's and 3 wire is for autos, OBD version has nothing to do with it. Just to let everybody know.
 

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it is easier if you already have a 2 pin IACV. I am simply interested in checking if it is truly impossible to make an OBD2 IACV work with an OBD1 ECU.
It works, got a 2000 2 wire being controlled by a P06 Manual trans.
 
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