What are all the reasons which could be causing a trac code 26, sub throttle valve not actuating? The A/C clutch / pulley also never seems to disengage.
Could this affect the idle?

Right now, my lexus (‘92 with trac) idles around 800 in park and 400 in gear with the AC off, and around 200 with the AC on. Perhaps the tachometer is off.

 

please do some searches, as this topic has been covered many times over. usually with the AC on brings the idle up to help the engine with the compressor load, not down. low idle can be many different things.

also check this:
https://www.clublexus.com/forums/ls-...capacitor.html