I locked your previous topic as you were asking the same questions over and over without doing your homework. As I said in your other thread, you need to read the MSExtra manual as the information you are asking about is already covered.

Just because there are 4 wires labeled IAC does not mean they are wired internally to function with the processor as idle air controller signals. The IAC stepper motor is not a Fast Idle valve used only during cold starts. It continually receives pulses to open or close the valve to appropriately adjust the idle speed. Instead of emailing symtech and expecting a delay, why not call them if the issue demands haste? If your MSII unit was not equipped for idle control, the board needs modification. You said that a couple of the IAC wires are already dedicated for ignition output and tacho output, so it will take some rewiring and configuration if you wish to have 4-wire stepper motor control.

You ask what will be the result without an IAC? Well, if you remove it, you are going to have a gaping vacuum leak and your motor will not function correctly.

Again the MS project and concepts are all about DIY - the manuals are available and everything is available through searching here and over at http://msextra.com/forums/index.php and reading the manual.

I will even throw you a bone.

http://msextra.com/doc/ms2extra/MS2-Extra_Conversion.htm#idle

http://msextra.com/doc/ms2extra/MS2-Extra_Conversion.htm#start_idle

No one is going to hold your hand on this, you need to be proactive and do the research yourself, especially since you mentioned no one in the immediate area is able to tune for you.

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2012 2500HD LML