Low Idle w/ Saturn tuned port EFI.

[Bruce Plecan]

-----Original Message-----
From: Shannen Durphey <shannen at mcn.net>
To: diy_efi at efi332.eng.ohio-state.edu <diy_efi at efi332.eng.ohio-state.edu>
Date: Monday, October 26, 1998 10:00 AM
Subject: Re: Low Idle w/ Saturn tuned port EFI.

(GM)
Actually all the screw-in IAC are adjustable.  BUT, be careful the anti
rotation
part is soft plastic, and easy to ruin.  It is much better to get one of the
stepper motor kits, and slow it down to use.  They are like $25 so unless
your
doing alot if IAC stuff no real reason to buy one.  The adjustment is "lost"
after the ecm does it first reset. The initial adjustment is to keep from
ruining it
when you first install it.
  Shorting A+B and turning the key on, begins to extend the pintle to it's
max
lenght.  So when you unplug it the IAC passage way is closed.
  When you turn the key off, the IAC continues to have power for a moment,
and parks in the whithdrawn posistion, ready for a cold start.
  The above is for a 747, of which I'm sure of, and probably applies to all
of
the gm ecms.
Cheers
Bruce

>Jemison Richard wrote:
>> I apologize in advance for bugging you folks with this but I've got a
>> feeling there's something dumb I've done that is precipitating this
problem.
>> I originally started having a really low idle (500 rpm or less in gear).
No
>> increase in revs w/ air on either.  So I checked my codes and the IAC was
>> indicated (now I know this meant the IAC was unable to correct the
problem).
>> At the time I took it to mean the IAC WAS the problem.  I replaced the
IAC.
>> In the IAC there were instruction stating the plunger should be no more
than
>> 1" extended.  I double checked this and it was right at 1 inch (it is
>> obviously adjustable.  You screw it in one way or the other - don't
remember
>> offhand).
>What is this?  The IAC is adjustable?  I've never seen that, but maybe
>so.
>Doesn't sound like the good old GM unit.
>OK, first question.  This idle spped is actually causing problems,
>correct?  Not just annoyingly low?
>Next, do you have access to a scantool?  What are IAC counts?
>Is there any chance you can forward the instructionsfrom the IAC?
>Shannen
>> Anyway, I've since discovered the coils were both weak.  I've replaced
both.
>> The sucker runs like blue blazes (for a Saturn - OK you Chevy guys!) but
the
>> idle isn't one bit better!  I tried increasing the idle with the idle
screw
>> (makes perfect sense to an old carb guy!), nothing.  So I backed the
screw
>> off completely.  Nothing.  Then I disconnected the IAC with the idle
screw
>> completely backed off (and this is what's got me thinking).  This thing
>> idles at about 2500 with no IAC and no idle screw setting!  The IAC is
>> actually REDUCING the RPM.  Geez, I can feel you guys out there on the
floor
>> rolling in uncontrolled laughter.  Go for it!  Just give me the answer!
>> I'm thinking if I reduce the plunger extension I'll increase my idle.  Am
I
>> anywhere close?  And if I'm not, where should I be looking!?  I've
changed
>> and checked plugs, changed wires and coils.  I've checked the wiring from
>> the coils to the PCM and have checked the PCM (according to the excellent
>> ;-^) documentation I have on hand) and it checks OK.
>> Thank you in advance for your assistance and if you've really enjoyed
this
>> unbridled level of incompetance I'll try to keep 'em coming! ha!
>> Rick
>> jemisonr at tce.com