High idle issue on VN 355 and IAC pinout

[VoodooVn]

Have you tried this https://forums.justcommodores.com.au/threads/reseting-vn-vp-ecu.111607/ ?

I have tried these without any luck

 

[Immortality]

Unplug and remove the IAC, measure the depth of the IAC port on the throttle body and extend the stepper motor pintle so it's just a bit longer than the depth of the port. Then refit the stepper motor (this should fully block the idle bypass passage). Then start the engine and see what the idle does and if possible adjust the throttle body butterflies so it idles 600-650rpm (assuming it's a mild build with a small cam) or to and idle speed 50-100rpm where you would expect it to idle (has it been tuned? What idle speed is commanded?). Then plug the IAC back in and see what the idle does.

 

[VoodooVn]

Unplug and remove the IAC, measure the depth of the IAC port on the throttle body and extend the stepper motor pintle so it's just a bit longer than the depth of the port. Then refit the stepper motor (this should fully block the idle bypass passage). Then start the engine and see what the idle does and if possible adjust the throttle body butterflies so it idles 600-650rpm (assuming it's a mild build with a small cam) or to and idle speed 50-100rpm where you would expect it to idle (has it been tuned? What idle speed is commanded?). Then plug the IAC back in and see what the idle does.

It has been tuned but I don’t know what idle speed is commanded. I know my engine won’t idle at 600-650 rpm. 355 cube, 10.8/1 comp with solid cam. I went back to my tuner On the weekend and he showed me on the laptop that the iac was commanding a high number of steps but the iac wasn’t opening. When I drive the car and slow to a stop it idles high at 2000 rpm and rpm only comes down after I come to a complete stop.

 

[Immortality]

Ok. I'd probably start at a 1000rpm with something like that.

 

[VoodooVn]

Ok. I'd probably start at a 1000rpm with something like that.

Yep it’s a lot happier around those revs . The throttle body is brand new. I previously had a Holley throttle body with a Chrysler style stepper motor and I had the same issue. Changed to the edelbrock as it has all GM sensors and iac but it didn’t change anything. I was told the IAC would work with factory IAC wiring positions but I’ll check it all based on the info I’ve got from you guys.

 

[Deuce]

Any chance of an air leak in a vac line or gasket?

 

[Immortality]

Have you tried swapping it out with an original Holden IAC stepper motor?

 

[VoodooVn]

Have you tried swapping it out with an original Holden IAC stepper motor?

No I haven’t. I’ve only just bought it and was hoping it would work out of the box being all GM sensors. I’ll definitely give it a go though if all else fails

 

[VoodooVn]

Any chance of an air leak in a vac line or gasket?

All new lines etc. I’ve checked for vac leaks and also there weren’t any manifold vac leaks when the engine was on the engine dyno. Was thinking that a vac leak would always be there also.

 

[vt6banger]

the holden IAC wont work in it if its a edelbrock 3878, the iac needle is way longer.