Written by insu (forum member)
Why clean your AAC Valve/ What does it do?
When your RB series motor is warmed up and idling it is your AAC valve which controls the amount of air entering your engine in order to control your idle. The best description I can think of for one of the things that your AAC valve does is if you were to sit in your car, stationary at idle and turn the steering wheel. The throttle blips in order to stop the power drain taken from the power steering stall the car. That blip was the AAC valve letting more air into the engine, bypassing the closed throttle body.
There has been much said about dirty/faulty AAC valves causing or attributing to idle hunting issues and this was my reasoning for cleaning my valve. This isn't the only cause of poor idle issues, but it can definitely attribute if not cause poor idle/ hunting idle issues.
Basically over years of use, carbon deposits rising from the engine, minute grit etc from the intake builds up around the valve and causes it to work in less than ideal conditions.
(Note, this is not the valve which controlls cold start revs on idle, that valve is connected inline on the same intake pipe as the AAC valve but is situated under the intake plenum on RB25's)
Check this thread out: great success in cleaning in it
http://www.skylinesaustralia.com/forums/in...howtopic=110431