My idle's been messed up lately, dipping low when I pop out the clutch coming to a stoplight for example, and I know it's a problem with a lot of higher mileage Subarus (IE bugeyes and peanuteyes). So I cleaned my idle air control valve for basically 10 bucks (gasket, rubbing alcohol and q-tips) and the car is back to running smooth as ever. Amazing difference for the little effort involved.

I know a lot of people here don't surf nasioc, so I wanted to point a link to this thread about it http://forums.nasioc.com/forums/showthread.php?t=781242

The valve actually stuck open a bit after I cleaned it, leading to a 6000rpm idle. Was all good after that wtf moment though.

 

what are peanut eyes?

 

the 04-05

 

Just to add another note, while this sometimes works, it can be dirtier where you actually have to disassemble the IACV. There's a thread somewhere on NASIOC that's linked in that thread, but I can't find it.

Basically, when you take the IACV off, there's 2 small torx screws (I think they're torx) that secure the motor to the valve. Be careful, it's fragile and easy to damage. Once the motor is off, try spinning the valve. Mine had so much junk in it, it wouldn't spin very easily, even though I cleaned it per the OP's nasioc link. Just get some cleaner and spin it carefully until it spins freely to get all the junk out. Reattach and reinstall. Also, if it still is idling funny, check for vacuum leaks and clean the MAF.