[Gmecm] Re: Closed loop and stalling

[Rick McLeod]

Nice write up, Jay! I would comment though that most
people belive that the minimum idle stop setting is
setting minimum idle RPM, but it really only sets
minimum throttle vain position, minimum RPM is
dependant on other items such as weatehr conditions,
hence the IAC taking over. I've set cars up one day
for a min idle, then checked a week later and seen
them off by as much as 25 rpm (nit-picking I agree)
but none the less it does wander over time/fuel.

Otherwise, great write up!! (compliments given where
compliments due!)

--- Jay Vessels <jay at vessels-clan.com> wrote:
> Hi there!
> 
> A quick writeup I did a while back on setting
> minimum air and TPS voltage:
> 
> http://s-series.org/Sections-article1-p1.html
> 
> On some ECMs, jumper A&B with the ignition off.  Key
> on, the IAC will 
> extend fully (give it a few seconds).  I usually
> just unplug the IAC at 
> this time, then start the engine.  Set the throttle
> stop screw to your 
> base idle speed (ECM won't be able to make it idle
> slower than this, 
> only faster), shut it down, then set the TPS voltage
> appropriately. 
> Don't forget to plug everything back in!
> 
> You're shooting for a TPS closed throttle voltage of
> .5V.  There's a bit 
> of slop in that but every GM ECM I've seen that uses
> an adjustable TPS 
> will accept .5V +/- 0.05V as a closed throttle
> voltage.
> 
> Jay Vessels
> 1982 Chevrolet S-10 Sport, 2.8V6 TBI
> 1984 Chevrolet S-10 Blazer Sport, 2.8V6 carb. (for
> now)
> 
> Frank McCracken wrote:
> > Rick;
> > Your suggestion to put it into diagnostic mode, is
> to jump A and B? And then
> > continue with procedure?
> > What do you set tps voltage at? I have conflcting
> voltage settings.
> > 747 ecm, 400sb, Holley tbi, manual shift.
> > Frank.
> > 
> > 
> > 
> > ----- Original Message -----
> > From: "Rick McLeod" <dunvegan at sbcglobal.net>
> > To: <gmecm at diy-efi.org>
> > Sent: Wednesday, May 25, 2005 9:57 AM
> > Subject: Re: [Gmecm] Re: Closed loop and stalling
> > 
> > 
> > 
> >>Most have a code that when in diag mode, they
> extend
> >>the pintle, so I place in that mode, wait, then
> remove
> >>connector, and then remove diag mode, start car,
> >>adjust idle to just below spec, restart after
> >>reconnecting IAC, and all is good. Works great on
> my
> >>TPI cars, and I also set TPS at the same time to
> make
> >>sure all is good, always get good off-idle resonse
> w/
> >>this procedure.
> >>
> >>
> >>--- Cowen <captain_krill at yahoo.com> wrote:
> >>
> >>>Oops.  When I described setting the idle stop
> screw
> >>>for proper idle, I forgot one step - actually I
> >>>still
> >>>forget it!  If I recall, before you begin, I
> believe
> >>>you have to pull the ECM fuse.  If you don't pull
> >>>the
> >>>fuse, when you switch the ignition ON, the IAC
> will
> >>>extend the pintle (as you want) but then pull it
> >>>back
> >>>again to the "start" position.
> >>>Pulling the ECM fuse forces the IAC to extend the
> >>>pintle fully, allowing you to set the idle with
> the
> >>>throttle plate only.  The IAC will have minimal
> >>>adjusting to do after that.  Be sure to replace
> the
> >>>fuse before starting the engine.  Sorry about the
> >>>omission!
> >>>
> >>>**********************END
> >>>TRANSMISSION**********************
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