Timing jump at idle

[Dave Zug]

aah, you beat me to the answer.  Scott S related this a very long time ago.

I wondered if it was a byproduct of the spark table having such large jumps
near the idle area or if there was a seperate, dedicated process for idle
assist.


----- Original Message -----
From: rr <RRauscher at nni.com>
To: <gmecm at diy-efi.org>
Sent: Friday, November 10, 2000 4:14 PM
Subject: Re: Timing jump at idle


>
> Some ecms/masks will vary timing to help control idle rpm. Maybe
> that is what you are seeing.
>
> BobR.
>
> Bob Valentine wrote:
>
> > I'm trying to figure out why my timing varies +/- about 4 degrees.
I've
> > flattened the table for several cells around in gear idle, 625rpm.  MAP
> > stays rock-steady at 35kpa.    Injector pw varies from 2.55-2.6ms.  The
> > idle is reasonably smooth no surging or misfire, but would be smoother
with
> > the timing stable.
> >
> > With the timing connector pulled and a timing light on the crank, the
mark
> > stays even on 6deg.   The mark moves and follows the scantool with the
EST
> > hooked up.  I changed the distributor (and module) since the one in the
> > motor had a slight bit of end play - no difference, same symptoms.
Plug
> > wires are routed as far from the harness as possible.    Disconnected
the
> > alternator to rule out AC noise, no difference.
> >
> > Is this "normal" or is something going on?
> >
> > -> Bob Valentine
> > -> bob at tecmark.com
>
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