Re: VSS question

["JN" <jwn@sgi.net>]

In my 89 Corvette I found out that a VSS means alot!  I actually had a
problem where my vss signal between the cluster and ecm was shorting out the
wire that goes to my ac clutch. the AC clutch would not engage until the car
moved!  When it did, it would pulse with the vss signal and fry the clutch.
Talk about a hard problem to find!  The car would stall at every light
because of a lack of vss.   Solution was to run a new wire from the ecm to
the cluster.

Jason
----- Original Message -----
From: "Mark Romans" <romans@pacbell.net>
To: <gmecm@efi332.eng.ohio-state.edu>
Sent: Tuesday, January 18, 2000 9:44 PM
Subject: Re: VSS question


> There are a few things in the code that look at vss.  Mainly if your
moving
> or not, doesn't matter how fast.  Off the top of my head, fan controls,
fans
> shut off at 35 mph, also idle stuff as you have found out.  If the engine
> speed goes below a certain rpm then the ecm goes faster to make sure the
> vehicle doesn't stall.  There are probably more.  DFCO, declleration fuel
> cut off. ect.
> Hook up a vss.
> Mark
> -----Original Message-----
> From: Andrew Choset <agc3@cornell.edu>
> To: gmecm@efi332.eng.ohio-state.edu <gmecm@efi332.eng.ohio-state.edu>
> Date: Tuesday, January 18, 2000 6:39 PM
> Subject: VSS question
>
>
> >In a manual transmission car with a cable driven speedo, and no cruise,
is
> >there any real purpose for the VSS?
> >
> >Background to my question--
> >
> >88 IROC-Z, L98, originally 700R4 with cable speedo.  Swapped in T56,
> >replaced speedo with AutoMeter electric speedo.  Stock speedo
incorporated
> >an IR pulse generator to feed a signal to the VSS buffer box.  As it sits
> >now, there is no pulse generator, and the VSS buffer box gets no signal,
> >therefore the ECM gets no VSS signal.  As a result, code 24 would set.
OK,
> >use a jumper to close the Park/Neutral switch, to fool the ECM into
> >believing that the 700R4 that no longer existed was always in park, and
> >therefore the ECM didn't look for any VSS input. Did the trick, no more
> >code 24.
> >
> >However, it soon became apparent that I've got an idle issue... upon
coming
> >to a stop (trans in neutral), the idle speed will often hang out around
> >1500rpm, sometimes even a little higher.  Is there a possibility that
this
> >is a result of not having a VSS input?  The problem does *not* occur
> >always, in fact, sometimes I'll go a week without having the problem.
> >
> >Any ideas?
> >
> >Thanks in advance.
> >
> >Andrew Choset
> >
> >
>