GM IAC valve question

[panel]

http://www.megamanual.com/ms2/IAC.htm

Does the GM stepper valve actually bottom out on the cone shaped bottom to the object it sits into?

[kjones6039]

Yeppers.........

When it bottoms out it should shut off idle air completely.

Ken

[grippo]

The best way to set it up is to let the IAC cone bottom out on the valve seat to close off all air, then let enough air in for desired hot idle speed by adjusting the throttle plate idle screw. If you can't do this, then you could set the motor steps so it doesn't fully close, but closes just enough to give you the desired hot idle speed. The only problem with this is thst the motor control may not be as repeatable as setting the screw. But you can make full closure of the valve repeatable by overextending the cone by a few steps, which won't hurt anything.

[panel]

Thanks guys! What I might do is make a fitting that one of these will fit into remotely. Then run some hose to the TB.

Any pics of what/where they are mounted on an OEM car?

[panel]

Nother question........

Does MS have the feature where these kind of valve's have the opening at cranking (and cold motor) where it's needed but then closed or almost closed when the car is cranking at full operating temp and maybe doesn't need the valve open as much or at all?

[panel]

Is this my answer to my above question?

Then at startup the motor will move to open (step=0), then immediately after go to whatever position is right based on the coolant temperature, say step = 50. This will all take place in about a second, probably before the engine ever fires. Then the motor will slowly move to the closed position as the coolant gets hot, which can be 110 if that is what is in your table of step vs. coolant temperature.

[downwardspiral]

Thanks guys! What I might do is make a fitting that one of these will fit into remotely. Then run some hose to the TB.

Any pics of what/where they are mounted on an OEM car?

I am using a northstar TB which is similar to this one (from a vortec motor). The IAC is in the TB.

[fury fan]

Thanks guys! What I might do is make a fitting that one of these will fit into remotely. Then run some hose to the TB.

Any pics of what/where they are mounted on an OEM car?

I don't have any pics handy, but I found that mid-90s GM 2.8/3.1 had the IAC mounted in a removable body on the intake tract. Looks like it should be do-able for a remote mount if you fab up a block-off plate and some hosebarb fittings.

[Six_Shooter]

When tuning the GM ECMs, it's recommended to have the IAC open by between 30 and 40 steps. This allows the IAC to close more if there seems to be a higher than commanded idle situation. It also helps with getting a smoother idle usually, in that the change in airflow is a smaller difference than going from completly closed to even slightly open.

I addition to the above mentioned 2.8/3.1, which you are looking for the 1987 to 1994 FWD genII 3.1, with the flat top intake manifold that says either "2.8 MPFI" or "3.1 MPFI", for the remoavable IAC housing. There are also some vacuum ports in this housing, that would need to be blocked as well. The genIII 3.1, AKA "3100" has a different throttle body that is cast as all one piece. I actually have one of these TBs on my Nissan L28 in my '73 240Z. They would be good to use to convert from some of the early Nissan (and other manufacturer) engines that used a throttle positions switch isntead of a variable sensor, you also get the IAC control in there as well, simple adaptor plate and you're in business.
Also take a look at the GM 3.4 DOHC engines, IIRC they have a real nice IAC housing that simple has ports for the IAC. Would still require some way to attach hoses to it, but is a nice starting point.

DIYAutoTune also seels a nice little block that uses the above pictured two screw type IAC (They say it's for the "Jeep style", but is the same, other than the direction the 4 pin connector points, once installed). It has hose barb fittings.

Edlebrock sells a GM IAC housing that is for using the Ford TBs, this would be a good base for IAC control. Like I said it's designed to bolt to Ford TBs, but could be addapted pretty easy using another block, to add some pipe threads to for barb fittings or in someother way for many applications.