2002 Subaru Legacy Wagon package

Subaru sets the idle especially low for emissions reasons before the 2008 PZEV era. It gets an auto-boost with AC powered on (defrost too), which may help you. That the trans- motor attachment bolt pattern isn't stiff enough causes a lumpiness too. First thoroughly spray-clean the interior bore of the throttle body. Replace old platinum plugs with newest iridium ones. If idle still submerges to 600rpm you can try loosening the attachment bolts on the idle control valve and rotating it very slightly to pick up 50- 100rpm. But if you go too far the ECM will trigger an error, submerge the idle again, and throw a new CEL, requiring that you erase the code and start the process over again. Be subtle here! But do clean things out first, as a gummy throttle body will indeed submerge idle speed. If nothing works keep your AC on and live with the depressed fuel eco. Good luck. Ern