ignition miss

[Bruce Plecan]

-----Original Message-----
From: Andrew F. Gunnesch <afgun at mongoose.dearborn.sgi.com>
To: third-gen at f-body.org <third-gen at f-body.org>;
diy_efi at efi332.eng.ohio-state.edu <diy_efi at efi332.eng.ohio-state.edu>
Date: Thursday, September 03, 1998 8:23 AM
Subject: Re: ignition miss


>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

Try setting everything to stock, and see how it runs.  Check fuel
pressure, at idle, and WOT.  Of course follow safety guide.
>
>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?

Disconnect the connector at the trans, and see if the problem goes
away.   Would at least rule the vss in or out.
If no difference, try unplugging MAF.

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
>