IAC Valve, how does it work and why?

From looking it takes in air from the PVC system or atleast the PVC system plugs in right next to it.

And I assume it does this to control the idle by adding more air or gases from the PVCsystem?

on my 2.8 one of the PVC hook to the air intake boot in front of the throtle body and the other one if you trace it ends up on the other side of the throtle body connecting next to the ICA valve.


Does the IAC need air rom the PVC system to work, could regular fresh air work.

or does the PVC just bleed into the air stream un interupted and the ICA does something else.

what does the IAC valve do really, do you even need it?

 

the idle air control valve is what controls the amount of air entering the motor when you are at zero throttle (throttle plate in the throttle body will be closed) the pintle moves in and out. yes you need the iac valve. hope that helps some. best of luck, tom

 

I'm not sure of the exact path for the 2.8 setup, but on the TPI V8's, the IAC works as a "controlled vacuum leak" to regulate idle speed.

With the throttle plates closed, the IAC will extend to lower the idle speed, while it's blocking off air from entering the intake...the reverse is tru for increasing idle speed, the IAC retracts, making the passage for air into the intake larger and allowing more air into the intake...the result is higher idle speed.

As noted above, yes you need it to maintain the EPROM's target idle speed, but if yours is bad, you could play a little (with it unplugged) starting from the fully extended position and moving it back to the motor (IAC motor) a bit at a time, to give you a somewhat decent idle.

That said, since it's kinda of a PIA to removed, replace, remove, replace, etc...may as just replace it with new if your's is bad.