Adding GM IAC with ITB setup | AEM
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Last seen: 4 years 11 months ago
Joined: 02/18/2015 - 17:32
Adding GM IAC with ITB setup

Hi, excited when I found this system.  Currently have it in a Cobra Replica show car we are building.  Has stock Coyote crate engine from Ford with Eight Stack ITB setup.  Pulled the trigger once I read could control VVT.  Anyway, we typically use a competitors remote IAC setup which essentially uses a GM 4 wire IAC.  Wondered if there is an easy way to add the wires and configure it in the initial tune.  First time using your system so figured some guidance could cut down my learning curve.  The system uses a throttle cable so I hooked the TPS signal wire to the TPS signal wire from throttle body vs the electronic gas pedal signal which I'm guessing is correct.  

I ordered some terminals for the ECU plug, but were incorrect.  I have some Molex Mx64 plugs on order that I haven't received yet that I think are the actual ones I need.

Thanks for any info

Last seen: 2 months 2 weeks ago
Joined: 06/07/2014 - 14:29
Coyote-powered Cobra replica

Coyote-powered Cobra replica sounds like a fun project. The Infinity ECU can work with a 4-wire stepper IAC, you will need to run new wires from the ECU connector to the IAC and then configure the software to know the max number of steps allowed.  


For wiring, you can use the instructions PDF from the Infinity Layover Harness: GM LS Engines 24X as a reference. That document is here:  , cliff notes are as follows:

Infinity pin C1-69 connects to    IAC pin B  (stepper Coil B+)

Infinity pin C1-70 connects to    IAC pin D  (stepper Coil A+)

Infinity pin C1-71 connects to    IAC pin A  (stepper Coil B-)

Infinity pin C1-72 connects to    IAC pin C  (stepper Coil A-)




Configuring the IAC max number of steps is described in the 'Infinity Full Manual' instructions PDF, available here:

Here is an excerpt:

Idle Setup: Stepper Idle Valves (For 2-wire PWM idle valves, or drive-by-wire vehicles, please skip ahead to the Idle Basic Setup section.)

When working with a 4-wire or 6-wire stepper idle valve, it is necessary for the ECU to know the correct value for Idle Stepper max steps before adjusting any other idle settings. The ECU can never measure a stepper valve's actual position, it can only command that the valve take steps up or steps down and remember how many steps have been commanded. To operate a stepper valve correctly, the ECU must know the maximum number of steps that can be commanded before hitting the mechanical stop. Please follow the instructions below to determine the correct value for Idle Stepper Max Steps on an unknown idle stepper motor.

1. With the engine off, remove accessory components as needed so the stepper valve's plunger is visible and/or it is possible to hear the sound of the stepper valve hitting its mechanical stop. Note that some setups use the engine's intake manifold or throttle body for the mechanical stop; when working with these setups, the stepper valve must remain connected to the mechanical stop.

2. Without changing the Idle Max Position, disable feedback by setting the Idle Feedback Min and Idle Feedback Max to 0%.

3. Set the IdleBasePosition to zero. When the commanded position is zero, the ECU's stepper output will take a few additional steps to ensure the stepper valve at the minimum position.

4. Press [CTRL+U] to increase the IdleBasePosition value one percent at a time, from 0 to 100. If you hear the idle valve hit the mechanical stop before the table value is 100 , your Idle Max Position is too high. If you do not hear the idle valve hit the mechanical stop, the Idle Max Position may be too low.

5. Increase the Idle Max Position value by one.

6. Reset the ECU (so it will park the idle valve).

7. Repeat the test again. The goal is to use most of the stepper’s possible range without letting the valve hit the stop


Last seen: 4 years 11 months ago
Joined: 02/18/2015 - 17:32
Thanks, thats essentially

Thanks, thats essentially what I needed reasurrance with.  Have a couple more questions, I'll make new posts as they apply differently.