This is topic why does it read that im going faster in forum Tech Talk at Northern California Ford Owners  .


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Posted by Sic Beast (Member # 6771) on :
 
I was in my 94 gt on the freeway with flow of traffic and I looked and it showed I was goin 90 mph. What can trigger this to make it seem I'm goin faster?
 
Posted by 95_svt_last_of_the_5.0 (Member # 9527) on :
 
gears??
 
Posted by jaejae (Member # 7958) on :
 
gears
 
Posted by Sic Beast (Member # 6771) on :
 
I thought that too..but itz all stock but exhaust headers and h pipe and flowz.
 
Posted by Blind (Member # 3052) on :
 
tires
 
Posted by MarkOlson (Member # 9556) on :
 
Check your VSS connections, especially ground.
 
Posted by Sic Beast (Member # 6771) on :
 
quote:
Originally posted by Blind:
tires
I have 18" cobras..but my cousin has 17" and is having similar problems.
 
Posted by Sic Beast (Member # 6771) on :
 
quote:
Originally posted by MarkOlson:
Check your VSS connections, especially ground.
Ok and where are those connectionz or what are they?
 
Posted by MarkOlson (Member # 9556) on :
 
If the speedo is always reading high, then it is not an electrical problem and you need to calculate your tire diameter and compare it to stock. If your tire diameter is smaller than stock, then your speedometer will read faster than you are actually going. If this is the case, you will need to put in a speedcal to correct the signal for the different tire diameter.

However, if the problem is intermittant, then the problem is probably electrical.

This is based on my 96 which I think is the same as yours, but I am not 100% positive. However I am 100% positive that your speedometer in the cluster is the same as my speedometer since I have 94, 95 & 97 clusters on my workbench at the moment.

On my car, the Vehicle Speed sensor is near the end of the tail of the tranny. There will be a connector on a gizmo bolted to the tail. That gizmo is the vehicle speed sensor. It puts out a signal that has 8000 pulses per mile.

That VSS signal goes to the PCM and to the speedo/odometer.

If your problem is intermittent, then it is probably an intermittant issue with a wire or connector vibrating, making the signal look like it is going faster than it should.

[ December 30, 2009, 12:38 PM: Message edited by: MarkOlson ]
 
Posted by Sic Beast (Member # 6771) on :
 
quote:
Originally posted by MarkOlson:
If the speedo is always reading high, then it is not an electrical problem and you need to calculate your tire diameter and compare it to stock. If your tire diameter is smaller than stock, then your speedometer will read faster than you are actually going. If this is the case, you will need to put in a speedcal to correct the signal for the different tire diameter.

However, if the problem is intermittant, then the problem is probably electrical.

This is based on my 96 which I think is the same as yours, but I am not 100% positive. However I am 100% positive that your speedometer in the cluster is the same as my speedometer since I have 94, 95 & 97 clusters on my workbench at the moment.

On my car, the Vehicle Speed sensor is near the end of the tail of the tranny. There will be a connector on a gizmo bolted to the tail. That gizmo is the vehicle speed sensor. It puts out a signal that has 8000 pulses per mile.

That VSS signal goes to the PCM and to the speedo/odometer.

If your problem is intermittent, then it is probably an intermittant issue with a wire or connector vibrating, making the signal look like it is going faster than it should.
Thankz man...really broke it down. Appreciate it. I'm goin to have to jack it up and take a look.
So if it is that wire or connector your saying...I have to change it if not loose?
 
Posted by MarkOlson (Member # 9556) on :
 
I wouldn't replace anything unless it is broken or corroded. Check out the connectors at the transmission, PCM and instrument cluster. If the connectors look broken or the contacts look corroded, then replace the connectors and/or what they connect to.

Look at all the the wires from the transmission to the PCM and cluster to look for melted or chafing wires.

If that doesn't find the issue, then you'll need to look deeper. How often does this happen? would it happen if you put the rear on jackstands and spun the wheels with a voltmeter on the VSS wire?
 




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