[Gmecm] Re: Closed loop and stalling

[Jay Vessels]

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**********************