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Crazy Speedometer *UPDATE*

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by jc71355, Feb 17, 2003.

  1. jc71355

    jc71355 1/2 ton status

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    I've got a problem with my 91. When I get to about 60-65 mph on my speedo (actual speed is off due to tires) my speedometer begins to bounce. A couple of times it went all the way to 30 or 35 and the truck sounded weird. The engine tone didn't sound right and it didn't feel like it had as much power. I tried putting it in OD vs D and it made no difference. I also went ahead and pushed on past to about 70-75 mph on the speedo and everything smoothed out like normal. Any one know what could be causeing this??? /forums/images/graemlins/1zhelp.gif
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    Re: Crazy Speedometer

    If the Vehicle Speed Sensor is sending incorrect data to the ECM, driveability will suffer. You probably have something going on in that area, since the speedometer is governed by the VSS.

    You'll need to troubleshoot though, there are a few things that can be wrong.
     
  3. jc71355

    jc71355 1/2 ton status

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    Re: Crazy Speedometer

    Thanks,
    Is there a way to test that VSS?
     
  4. jc71355

    jc71355 1/2 ton status

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    Re: Crazy Speedometer

    I had ATF in the plug that was making it act crazzy.
     
  5. dyeager535

    dyeager535 1 ton status Premium Member

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    Re: Crazy Speedometer

    Yep. Hook a scanner up to it. It'll tell you what speed you are going. If the scanner reads wrong, the VSS is delivering incorrect data.
     

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