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

[Cowen]

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

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