I own a MY98 Impreza STi fitted with S6PNP and decided to implant a MY04 STI 2.5 forged engine. After considering MY99 manifold and the option of losing 4 outputs for the stepper motor I decided to use 2.0 MY03 intake manifold, throttle body and coils.
The question is what settings should I use for the IAC valve?
My guess would be 244hz frequency and Active High polarity (similar to MY98 settings).
Unfortunately it is not working as supposed and I was wondering whether my setting are incorrect or the valve is simply dirty/faulty.
Thanks!
Subaru IAC valve
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pat
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Re: Subaru IAC valve
The ISCs are rather different between the MY98 and the MY01-05, but fortunately enough for you, compatible with a little bit of wiring 
The original item is a centre tapped bidirectional rotational actuator, which means that +12V goes in on the centre pin and then the other two pins are PWMed to move the ISC in either direction away from its rest position. Presently we only drive one side on the S6PnP but the wiring is there to drive both sides, but this hasn't proven to be necessary yet so the support for bidirectional TBV control is presently on the low priority ToDo list....
Back on topic, the MY01-05 ISC is a linear servo-valve. As such it requires a +12V, a Ground and a control signal. You can use the original +12V, put an eyelet on the Ground wire and bolt that down using one of the two bolts that hold the ISC onto the throttle body, and finally you use one of the two control wires from the original. The output should be set to 1kHz PWM, polarity should be active low if memory serves. That type of servovalve is a prone to getting gummed up but is easy enough to free up again... the only gotcha is that the bolts that hold the stator onto the valve body are 5 pointed Torx, but they can be removed by careful use of a set of long nose mole grips if you don't have the necessary bit. The rotor should rotate freely but it probably won't. Fix this by pouring brake cleaner into the cavity and rotating the rotor by rolling it along your index finger. After a while it will suddenly free up. When this happen, spin it a few more turns, then drain out the brake cleaner and replace with WD40 or similar, then work the penetrating oil into the bearing. Drain the excess, and re-fit the stator, taking care to get the tang on the end of the magnet into its slot in the stator.
There's no guarantee that you'll have picked the right control wire, so set the base idle duty quite low and see if it affects the idle, if it does then it is the right one, if not then re-assign the TBV output to the other injector, that is if it was originally on INJ7 then set it to INJ8 or vice versa. If the low duty does affect the idle but raises it instead of lowering it then you may need to set the output to active high.
Hope this helps,
Pat.
The original item is a centre tapped bidirectional rotational actuator, which means that +12V goes in on the centre pin and then the other two pins are PWMed to move the ISC in either direction away from its rest position. Presently we only drive one side on the S6PnP but the wiring is there to drive both sides, but this hasn't proven to be necessary yet so the support for bidirectional TBV control is presently on the low priority ToDo list....
Back on topic, the MY01-05 ISC is a linear servo-valve. As such it requires a +12V, a Ground and a control signal. You can use the original +12V, put an eyelet on the Ground wire and bolt that down using one of the two bolts that hold the ISC onto the throttle body, and finally you use one of the two control wires from the original. The output should be set to 1kHz PWM, polarity should be active low if memory serves. That type of servovalve is a prone to getting gummed up but is easy enough to free up again... the only gotcha is that the bolts that hold the stator onto the valve body are 5 pointed Torx, but they can be removed by careful use of a set of long nose mole grips if you don't have the necessary bit. The rotor should rotate freely but it probably won't. Fix this by pouring brake cleaner into the cavity and rotating the rotor by rolling it along your index finger. After a while it will suddenly free up. When this happen, spin it a few more turns, then drain out the brake cleaner and replace with WD40 or similar, then work the penetrating oil into the bearing. Drain the excess, and re-fit the stator, taking care to get the tang on the end of the magnet into its slot in the stator.
There's no guarantee that you'll have picked the right control wire, so set the base idle duty quite low and see if it affects the idle, if it does then it is the right one, if not then re-assign the TBV output to the other injector, that is if it was originally on INJ7 then set it to INJ8 or vice versa. If the low duty does affect the idle but raises it instead of lowering it then you may need to set the output to active high.
Hope this helps,
Pat.
Re: Subaru IAC valve
Thanks Pat!
It turns out that my IACV is damaged - the shaft is bent slightly and a piece of the magnet is missing. However, with a little bit of luck and your thorough instructions I got it working until I buy a replacement. 1 kHz and Active Low worked like a charm.
It turns out that my IACV is damaged - the shaft is bent slightly and a piece of the magnet is missing. However, with a little bit of luck and your thorough instructions I got it working until I buy a replacement. 1 kHz and Active Low worked like a charm.