ignition miss

[Andrew F. Gunnesch]

Subject: Re: ignition miss
> I have a 1989 TransAm GTA with the 5.7L MAF TPI.  I believe it's
> a 165 ECM, right?  :)
>
> well, having a problem...  the other day I re-timed my car.  set
> the timing back about 3-4 degrees to make the pinging go higher in the

Ok, here's some more data points...  today on the way to work the miss
was very mild, almost non-existant for the most part.

However, the speedometer was still doing the wild thang, jumping up
every few seconds.  As an experiment I engaged the cruise control and
the car went crazy with the speedometer's movement.

So...  it looks like a problem with the VSS buffer box or VSS input is
part of my likely culprit.  To get some more information, what does the
ECM in my car use VSS for?  Maybe it's thinking that somehow the car is
going past the speed cutoff and cutting out my ignition or injectors?
That would explain a lot...  anybody know how much a VSS buffer box
from a wrecking yard would be?

I'm hopefully going to get a diacom this weekend from my buddy so that I
can do some investigation before I just go blindly swapping parts :-/

Thanks for your input,

--andrew