[Gmecm] Re: Vortec L31 oscillating at idle

[Darren Freed]

I didn't have a 3.4 DOHC calibration, so I started with a 3.1 and went from
there (I've only recently managed to get a 1997 3.4 DOHC PCM off ebay).  In
addition, I changed the cam timing, which obviously didn't help.  Any
modification that affects airflow will affect the idle.  Getting the idle
right on an OBD-II PCM can be a real challenge, especially when you've got
as heavily a modified setup as mine.  I suppose I should write an article
for the wiki...  I'll add that to my to-do list!

Darren


On 3/19/07, Steve Ravet <Steve.Ravet at arm.com> wrote:
>
> Darren, this mismatch was in your stock calibration?  Or you
> inadvertently created a mismatch?  Or the engine was modified from stock
> to create the mismatch?
>
> --steve
>
> > -----Original Message-----
> > From: gmecm-bounces at diy-efi.org
> > [mailto:gmecm-bounces at diy-efi.org] On Behalf Of Darren Freed
> > Sent: Monday, March 19, 2007 9:59 AM
> > To: gmecm at diy-efi.org
> > Subject: Re: [Gmecm] Re: Vortec L31 oscillating at idle
> >
> > I had the same idle problem with my 3.4 DOHC v6.  This
> > problem occurs because there is a discrepancy between the
> > desired idle rpm and desired idle airflow values.  The OBD-II
> > idle algorithm is very different than the OBD-I
> > algorithm: both desired rpm and desired airflow are used.  If
> > they disagree, the IAC hunts for an idle speed that will
> > satisfy both criteria.  The only way to fix the problem is to
> > change the desired airflow and/or rpm tables in the flashrom.
> >  Hopefully you can do that with OBD-II TunerCat.
> >
> > HTH,
> >
> > Darren
> >
>
> --
> IMPORTANT NOTICE: The contents of this email and any attachments are
> confidential and may also be privileged. If you are not the intended
> recipient, please notify the sender immediately and do not disclose the
> contents to any other person, use it for any purpose, or store or copy the
> information in any medium.  Thank you.
>
>
> _______________________________________________
> Gmecm mailing list
> Gmecm at diy-efi.org
> Subscribe: http://lists.diy-efi.org/mailman/listinfo/gmecm
> Main WWW page: http://www.diy-efi.org/gmecm
>