91 MT IAC?

[moelawe]

I have a '91 EJ22 in a VW Vanagon that came from a JDM Legacy. I have been having rough idle issues for about a year and I have tried everything that I can think of. Thanks to you fine folks, I have been able to trace the issue to the IACV solenoid. As I am sure you all know, the 91 MT IACV is a short-run part (I believe only 90-91) and I am having a difficult time tracking down a replacement solenoid. Also, the '91 MT two prong IACV solenoid is only compatible with the Hitachi ECU.

I do have access to a 92 or 93 parts Legacy with the three prong IACV and the JECS ECU to match (the car is also a manual). My question is: Is it possible to swap the IACV (valve and solenoid) from the 92/93 as well as the JECS ECU from the 92/93 into my van and not cause myself a lot of issues? Thank you in advance!

[rallyak]

I too have a 90 MT with the same IAC and I did what your thinking of doing. I changed the ECM from a 93 legacy, the IAC and the MAF to match. All my idle issues went away and runs like a different car. I should have done it years ago. I didn’t have any issues with wiring it was completely plug and play.

[moelawe]

Thank you for your help! Looks like I'm headed to the scrap yard today.

[carfreak85]

Why not just clean the IAC? There are several tutorials out there both for the legacy and the later imprezas. It's pretty darn easy.

[Legacy777]

The injectors are also different between ECU's and you really should change the injectors.

My suggestion would be to get the IAC, ECU, MAF, & injectors with fuel rails.

[rallyak]

Yes, the injectors are different but air/fuel is still on the rich side even though the gray ones are smaller. In my car I’ve cleaned the IACV hundreds of times along with the two small springs and the solenoid on the top. I have a few laying around and tried three different ones and never seem to work properly. Not sure why Subaru made an odd ball IAC for 5 speed cars in 90-91.