94 Buick LaSabre Hi Idle and no Speedometer

[Shannen Durphey]

Russ & Renee Pelfrey wrote:
> 
> I have a 94 Buick LaSabre 92k miles 3.8L engine, OBD-1 compliant but with OBD-II Connector.  The pin outs used in the connector are 4,5,8,9,14,16.
> 
> Problem:
> 
> Last week the Ser. Eng. lamp came on and the speedometer stopped working along with the cruise control.  Also, the engine idles very high.  prob. at about 3k rpm.  I have replace the VSS to no avail. Please advise, I don't want to pay $600 for 30 min and a $50 part.
>
If you know of a shop that's charging $1200/hr as a labor rate, please tell me. 
I need to pack up my tools and change jobs.

You will want to invest in a good service reference, which can be anywhere from
$15 to $75, depending on what manuals you get and where you buy them from. 
You'll want to get a good multimeter, which typically costs around $300 but can
be as high as $600.  You'll want to dedicate the better part of a day because
electrical problems can be anything from a 5 job to something that requires in
excess of 6 hours to find.  If you have more experience the problem can be
easier to find, but I think you may want to "spend" the entire day for this
problem.  I can't put a dollar amount on that, but you I'd expect that you make
at least $10/hr so we can say the value of your time is no less than $60. 
You'll also want to have miscellaneous hand tools around for electrical repairs,
parts replacement & etc which will add to the cost of doing the job yourself.

Remember that the above list includes the tools that a professional mechanic
needs to be able to fix a car that comes into his shop, and remember also that
the shop he works for needs to charge enough to stay in business.  
Remember also that the repair businesses which you are trying not to pay are the
very reason that there are people around who have the information you need to
fix your car.

With that said, it sounds like you have no speed sensor signal.  You will want
to use a scope or multimeter to see if the speed sensor you've installed is
generating a signal.  The signal is an A/C wave which will change in frequency
and voltage as tire speed increases.  You can lift the car onto jackstands and
place it in gear to check this.  If you have no signal from the speed sensor,
you'll need to physically remove it and check to make sure the drive/driven gear
or the reluctor ring is ok.  If you have a signal at the sensor, you'll want to
check for a signal at the ecm.  This is where the good service manual will
really help.  You'll want to use your meter or scope to check for a signal
similar to the one you saw at the vss.  If no signal, you'll probably want to
check the wires from the vss to the ecm for opens/shorts.  If you have a signal,
you'll want to check the terminals in the ecm connector and in the ecm for
damage, misalignment, corrosion, and generally poor condition.  If everything
checks out, the odds are pretty good that you have a bad ecm.

But all of this could be untrue because GM sometimes sends the speed signal to a
buffer box or to the instrument panel before the ecm.  So you'll really want to
look through a factory service manual or another good reference to see how the
vss is wired up.  You can use the Alldata web site 
http://www.alldata.com/vehicle_owner/index.html

to locate an Alldata shop near you.  They often print up schematics and
diagnostic pages for a small fee.
Shannen
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