[Gmecm] IAC / AIS Setup - $8D/7730 )

[Gary Evans]

I agree with Duncan - I had a similar expereince with my setup (dual  
3.1 ecms on jag V12). The car would sometimes stall during decel  
because IAC counts could drop too low while the car was moving.

Set the throttle plate to provide the minimum *desired* idle speed  
(e.g. 700 rpm), not the minimum possible idle speed. This will give  
the IAC the most room for adjusting the idle speed upward.

Bonus feature of this setting is that if you develop a vacuum leak  
you will be alerted to it by a too-high idle rather than allowing the  
IAC to compensate and cover up a potential problem.




On Apr 5, 2007, at 12:19 PM, Cowen wrote:

> I know the IAC setting procedure varies, and I've seen
> it described different ways for the same car (but from

> different sources) too.  That said however, I've got a
> 7730 in my cobbled together system, and what you
> describe is very different from what I've read.  In
> fact, what you've described caused serious problems on
> mine when I first got it going.
>
> I'm using a throttle body from a 2.8l, and an an ECM
> from a 3.1l, onto a 3.4l.  The point is, when I
> initially started it, the throttle body was set to run
> a 2.8l fine.  Now, for a given RPM, a 3.4l requires
> more airflow than a 2.8l. (3.4-2.8)/2.8=21% more air
> required.  Wow!  Although the IAC compensated, it
> didn't run well.  It felt like it had no torque,
> requiring high revs start the Jeep moving.  It had a
> huge bog on acceleration.  The reason?  As my foot
> advanced the throttle, the ECM was closing the IAC -
> and the two efforts canceled each other out!  Simply
> resetting the butterfly in the throttle body made an
> incredible improvement!
>
> Now, consider how you've set things up.  Your idle
> should be about 700-750, but you're setting the
> butterfly for about 400.  Best case scenario,
> (700-400)/400=43% The IAC must provide 43% more air
> than the butterfly to get the idle at 700!  If your
> setup works anything like mine did, it's no wonder
> things aren't working right!
>
> Solution?  If I recall, this is the procedure to set
> it with your 7730:
>
> 1. Jump the pins on the ALDL to trigger MIL flashes.
> 2. Key On, Engine Off.  These two steps force the IAC
> pintle to extend fully, so IAC can have no effect on
> idle.  You should hear the IAC running, trying to
> extend the pintle forever!
> 3. Unplug IAC.
> 4. Key Off, remove ALDL jumper.
> 5. Start engine (may require a foot on the gas if
> butterfly is really closed), and set butterfly to
> provide 700RPM idle.
> 6. Reconnect IAC.
>
> Good luck!
>
> Duncan
>
> **********************END TRANSMISSION**********************
>
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