86bird_28v6_5spd_ramair

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?

CaliCamaroRS

First off, PCV not PVC.

The IAC...Of course you need it!!!! Stop trying to eliminate things off your car. They all have a purpose. If the engineer of your motor felt it needed an IAC, then dammit, it needs an IAC.

When you're idleing, the throttle blade is COMPLETELY CLOSED. Now, considering the fact that AIR is semi-important to an internal combustion engine, how do you suppose an engine gets air with the throttle completely closed??? The IAC of course. It involves a pintle that can move in and out and control the amount of air flow at idle. If you turn on your A/C, the IAC will open up a little bit more to allow the motor to idle higher and compensate for the compressor load. Same goes for the power steering pressure switch.

The hose to the intake duct is simply a crankcase vent hose. No performance gained or lost by this hose.

TomP

LOL! I always tried the same thing when I first got into my engine... hm... EGR, do I need it?

The IAC gets it's air by using the hole in the passenger side front of the throttle body. If you remove the TB hose, look at the passenger side of the "uncovered" TB. There's a small hole there. You can do searches on this V6 forum for "IAC passageway", that's how the IAC is "fed" incoming air. When that passage clogs up with carbon, that's when the idle gets poor, since the IAC has less air to work with. The IAC lets that air thru directly behind the TB plates. It's just coincidence you see a big black plastic hose "near" the back of the TB. And that big black hose is a vacuum line, not a fresh air line... but yeah, it does connect to the PCV valve, and then connects to the intake manifold. You can see it being replaced by a red rubber heater hose here: http://www.geocities.com/tomp_3rdgen


And Dan, thanks for that bit of info regarding the IAC's position and the a/c//p/s switches, I didn't know that.

86bird_28v6_5spd_ramair

well that makes sense, i have that thing where my brain is faster than my fingers and they are lazy and take short cuts and some fingers get where they need to be before the other one.

if you go back to the EGR thread you will see why I dont like the PVC connecting there.

If I could re route the PVC and just give the IAC clean air is what I am after.


I see no need for alot of that "krap" all I need is spark, fuel, and air. I do not like how dirty the intake system gets.

CaliCamaroRS

No prob Tom. Just a note though; you'll only find a Power Steering Pressure Switch on smaller displacement engines. Bigger engines produce more power and usually aren't affected by PS pump load. Also, on bigger engines, you won't see much change in idle with the A/C on for the same reasons. I've only noticed a large change in idle on I4's and small V6's(such as our 60* 6ers).

TomP

I always figured I could use that p/s pressure switch to pass emissions, since it does raise the idle... might be something to keep in mind. Is that how it raises the idle speed? By opening up the IAC valve?

FAST RS

While we are tlaking about the IAC i got a new one for my car AC Delco i installed it and my car kept revving up and down and up and down then i put the old one in and it was fine is there somethign i need to do to get it to set right i didnt reset the computer im thinking that could be it any other ideas?

TomP

Sounds like you could take the new one back, 'cause your old one still works? Did you adjust the pintle on the new unit? If the IAC valve is over-extended, it won't adjust properly. I think the IAC reset procedure is part of the "IAC and TPS adjustment" article in thirdgen.org's tech section.