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I've got an EJ25 SOHC engine out of an automatic 2000 Outback that I plan to steel the heads off of. I'd like to take the intake manifold too and run that with the newer top feed injectors. The manifold looks like it's got some improvements too. My issue is IAC. On the late model cars the IAC is built into the throttle body. This one in particular has a 6 wire setup (seems odd) I guess manual trans cars had a different TB with less wires (4 I think). Is there any way of getting this to work on the stock 1990 EJ22 NA ECU? I couldn't find a wiring diagram for the 2000 IAC so I'm not sure why it even has 6 wires. What's my options here?

so anyone have any input on this? What about running it in a 95 Legacy manual. There's a pretty mint 95 wagon at the salvage auction next week with a clean title, I might pick it up seeng as I need a new engine and all anyway. That should have the newer Jecs engine management.

I don't know anything about the newer IAC valves, so this is speculation, but:

If it's got 6 wires it's probably a stepper motor. There's no way you'll get your 90 NA MT ECU to drive it.

You might be able to just go back to the stone age and not use IAC. You could use the throttle stop screw to get the kind of idle speed you want, and use a resistor to trick the ECU into thinking the valve's still there.

If the 2000 IAC valve has the same mechanical bimetal-strip-controlled valve functionality that ours have, then you'd still maintain high idle when cold. I don't know if it does, though.

The 95 Legacy's stock IAC valve is pretty much the same as on all first-generations except 90-91 NA MTs. Its ECU won't know how to drive the 2000 valve either.

But in any case, to use those heads, you'll have to figure something out, since I'm pretty sure your stock intake manifold won't fit the EJ25 SOHC heads.

yeah, it's a stepper motor... I might try to find a way to fab the stock IAC into a housing where the IAC goes on the newer TB... or I could just cut and weld the IAC housing off my original mani onto the new one.... kinda stinks though, I was hoping this would be simpler.

Did any scoobs come with an IAC in the TB that is compatable? What about late model manual trans cars?

I don't know for sure. I think early EJ18s had 3-wire IAC valves in the throttle body.

vrg3 wrote:I don't know for sure. I think early EJ18s had 3-wire IAC valves in the throttle body.

That is correct. i think. This is an interesting line of thought that I had never considered before. I've got both 1.8l and 2.2l manifolds and TB's lying around. I'll take a look at them and see what I can sort out.

He'll definitely need to run the SOHC Ej25 manifold, like you said, but maybe a 1.8l TB w/IAC could be made to work instead of the RS TB...

Oh, I have a MY00 FSM, and I'll try to remember to look at the wiring for it. I also have a '94 1.8l FSM and the Leggy FSM from here as well. I have become really intimate with them over the last 2 weeks. I can compare this stuff from model to model when I find some time. Just give me a few days since AZ2nr is gonna strangle me if I don't finish his harness conversion in short order...

I have alldata, so I can look at the wiring for any car, I just need to know the year/model that I should be looking at. I'll take a peak at the 94 EJ18 and see what it looks like. Maybe I can grab one at a local scrapper

Cool,
Saves me the effort since I don't really have a way to pass FSM's to other people who might need them. Let me know what you come up with. I may need this info at a later date.

'94-95 EJ18 Impreza would be the right era...

so I checked alldata for IAC info on a 95 EJ18 Impreza and yup, IAC is on the throttle body and it looks like it's got the same connector as the IAC for the EJ22. Looks like this thing will probable work. The one other bit of info that I need is to know what the TB size is for the EJ18. If it's smaller than the EJ22 I'm not sure what I'll do.

So anyone have a TB off an EJ18 that they can get the butterfly diameter from?

My buddy is building an EJ18 in my garage this weekend. I'll compare it to one of the Ej22 manifolds I have sitting around...

I'm pretty sure the EJ18 and EJ22 throttle bodies have the same bore.

Your pre-facelift 5MT NA ECU won't know how to drive any 3-wire IAC valve, but maybe you could switch to a post-facelift ECU.

I might be picking up a 95 wagon so I'll run it on that ECU... I do have a 94 ECU I could use too if I needed.

You'd probably be better off with the 94 ECU, since it's OBD-I (allowing you to pull codes without a scantool, and allowing you to use my scantool) and since it'll plug right into your harness.

Just be sure to use the harness from your stock intake manifold.