Having trouble with IAC

[legacymax]

I have an ej20g swap in my 94 turbo legacy wagon. I am using the stock ecu with 02+ wrx coils. The IAC is a turbo legacy top part(the part you turn to adjust the IAC) with a EJ20g bottom half.

When my car is warm and i come off the throttle, it will drop to about 700RPM and then slowly rise to about 2500RPM. Anyone had this problem before?

The car doesn't idle if i start it up and it is cold unless I adjust the IAC. But if I adjust the IAC, it wouldn't Idle well when it is warm.

I am wondering if it matters which way the IAC top part faces ( turned around 180 degrees).
-Max

[Legacy777]

Why did you swap the top piece anyway? They should be the same connector between the US & Ej20G engine.

[vrg3]

It does matter, I think. If you have it mounted backwards, maybe you could switch the outer two wires, though. That might make it work as it's supposed to again.

[Legacy777]

I agree with that.

[legacymax]

Why did you swap the top piece anyway? They should be the same connector between the US & Ej20G engine.

I was told that you need to match the IAC with the ECU, so a EJ20g IAC would not work with a T-leg ECU. Is this correct?

I can mount the top part each way, it is just a bit easier one way than the other and the ej20g IAC was mounted reverse to the US t-leg units.
I am just trying to get it idle like normal and I am working on finding the sweet spot between adjusting the TPS and IAC. Thanks for you guys' help.
-Max

[Legacy777]

I don't see why you can't use an EJ20g IAC with a tleg ECU.

With the IAC valves, they are essentially an electro magnet. current on one side moves the valve open......current on the other side moves the valve close. If you go and alter the position of the top connector peice you've now changed which side does the opening and which side does the closing.

You can change this by swapping/verifying the OPEN & CLOSE pin at the ECU. You need to make sure this is correct, regardless of which IAC valve you use.

Please don't take this the wrong way, but the IAC really is not adjustable. It's calibrated from the factory, and adjusting it just makes things out of calibration, and could cause you other problems.

As for the TPS, there's only one correct way to calibrate it. That's using the following procedure.
http://www.main.experiencetherave.com/s ... sting3.jpg

[BXSS]

I have a EJ20G in my SS running off the ej22t ECU.

I just plugged all the EJ20G sensors into the ej22t enigine harness, everything plugged in*.....

* - I just separated & the IAC wires from the harness to get a little more length with no splicing, & I used the ej22t cam & crank sensors as the WRX EJ20Gs have the newer style cam/crank sensors (Legacy EJ20Gs have the old style cam/crank sensors).

[jefferson]

I would go in and replace all the vacuum lines with new. Sometimes a connection will feel tight enough and still be leaking. Vacuum line is cheap.

I second the fuel injector cleaner also. I swear by Chevron techron. It's recommended by BMW, Mercedes, etal. It has gotten me out of some problems before on several occasions.

Another thing to do would be to clean all your grounds real good and make sure you have a good connection there.

Jeff

[legacymax]

Okay, I will try the EJ20g IAC than.
-Max

[smh0101]

Did you ever come up with a solution? I had the same problem only I was using a 20g IAC top part...

I ended up saying screw it and deleted IAC all together...

[impreza_GC8]

Mine does some funny idling sometimes too but I am currently in the process of cleaning it out and replacing it with a new gasket. The coolant lines on my IAC have been bypassed too, I'm wondering if that could have anything to do with it.