[Gmecm] Help with unusual BLM's

[Randy & Gene]

   On my 93 Pontiac Sunbird with a 3.1 V6 I found a badly shielded cable
between the  crank sensor and the electronic ignition module,, tac was all
over the place. It's shielded with foil like on a cigarette package that
breaks down over time. It took a few hours to remove but after being wrapped
with tin foil it works like new and no more tac swing and rough engine. RFI
gets into the ECU and interfers with other signals. Good Luck...Gene

----- Original Message ----- 
From: "Mike V" <efi at dyakron.com>
To: <gmecm at diy-efi.org>
Sent: Tuesday, April 04, 2006 9:29 AM
Subject: Re: [Gmecm] Help with unusual BLM's


I had these symptoms with a bad set of ignition wires.
The big clue is that it happened under load (higher cylinder pressures).
It also occurred more in wet / rainy weather.
It would missfire and the tach needle would drop.
MV

At 11:38 PM 4/3/2006 -0400, you wrote:
>This may not be correct, but the few times I have had a jumping (or
>dropping) tach, it has been an ignition module problem.   Its only been on
>GM V6 motors with DIS, but have done it with both a  3.1 and a 3.8.
>Replacing the module has solved my problem.    Just food for thought...
>
>Scott
>----- Original Message -----
>From: <ahuxtable at sola.com.au>
>To: <gmecm at diy-efi.org>
>Sent: Monday, April 03, 2006 7:01 PM
>Subject: RE: [Gmecm] Help with unusual BLM's
>
>
> > Thanks for the extra info Dustin.
> >
> > The misfire is really intermittent.  Plug gaps were triple checked and
> > the coil has also been replaced.
> >
> > Along with the misfire there is also a violent act of the tacho dropping
> > down.  This leads me more to thing that it could be something like the
> > coil/ignition module losing power (or the ECM altogether).  It's a sort
> > of CBF factor as it's ok most of the time.
> >
> > On a slightly different note however - It seems to be *almost* perfect
> > over the last few days while I've had the 10k resister in the ALDL
> > connector (logging or not).  Maybe it is the ECM after all...Then again,
> > it could be complete coincidence since the weather here has just taken a
> > bit of a cold snap.
> >
> >
> > Ahh, I love cars...
> >
> > Andrew
> >

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