MicroSquirt.com read only forum (Jan.15,2018)

EDIT: Below is my original post where I could not get it to work while bench testing. Please see the rest of the thread for what I was doing wrong.

Hi,

I picked up a Borg Warner IAC valve (#22971, 2 wire, for a Crown Vic ) to play around with on my DIYPNP. So far I am unable to get the valve to do anything but buzz at various frequencies. There seems to be no movement of the valve under any condition when using the idle valve test feature and varying the "run" IAC steps from 0 to 100, only changes in the audible buzzing. Have tried frequencies from 30hz to 300hz in the 30-something hz steps allowed.

The IAC valve:



Connector:



The FB Diode in place to the 12v IAC:



I'm starting to wonder if this IAC valve I'm using is bad?

I am bench testing with the DIYPNP hooked up to a PC and the aux 12v for power. I am applying 12v from the board (12v jumper hole) to one side of the valve connector, and my IAC jumper to the other side. I have tried reversing polarity to the same effect. I can confirm that resistance between ground and the IAC jumper varies from ~inf to 0 as I vary the Idle PWM% with the idle valve test.

Thoughts?

I found an old post on this forum that suggests this valve must have vacuum being pulled through it to actually close? Is that possible? Bugger.... didn't think of that.

Wonder if my vacuum cleaner can suck hard enough for bench test...

I hooked the valve up to the intake manifold and sure enough, the manifold vacuum was required to close the valve, at which point varying PWM has the desired effect of actuating the valve. Phew!

So the lesson is: A PWM IAC valve from a Crown Vic requires vacuum to seat, and thus requires vacuum to test actuation.

Another note: The valve requires a decent rate of flow to seat itself, I found that it was necessary to use a manifold port with no less than a 3/8" internal aperature and 1/2" hosing. I will post pics later showing how I am adapting this IAC valve to the hosing and how it is being mounted.

Couple of additional notes:

• The valve responds best at approx 120hz
• Too high a frequency and the valve never seats under vacuum after being opened
• Too low a frequency and the valve loses granularity (e.g., 31% = 700rpm idle, 32% = 1000rpm idle)
• Adapting this to a manifold that had no IAC valve meant using an existing vacuum port. I first tried to use the largest port available which the brake booster was hooked up to. What I did was run the IAC valve into this line and tee off that line to the brake booster. THIS CAUSED PROBLEMS WITH THE BRAKE BOOSTER where it would loose vacuum (and assisted braking!) when the valve was open! I ended up moving the brake booster to another manifold port and leaving this IAC valve attached by itself to the largest port availabe (~3/8"). I would recommend drilling and tapping a new large (1/2" ID at least) port into your manifold for use with an IAC valve such as this.

Note that this is on a 2.4l 22RE Motor.