My Speedo jumps to 80mph while ideling, should I be concerned?

[Eric 97LT4SS]

From time to time my Speedo will just jump from 0 to 80 mph while sitting at a traffic light, should I be concerned? The motor does not rev and no codes or SES light so what gives? My PCM has a three year old Superchips program but everything else seems to be functioning properly.

Thanks,
1997 Camaro SS LT4 # 093

[Joe 1320]

Faulty vehicle speed sensor? I would hook up a scanner and see if the speed sensor is triggering the jump in the gauge.

[Eric 97LT4SS]

Joe,

Thanks for the reply, do you know where the Vehicle Speed Sensor is located?

Thanks,
1997 Camaro SS LT4 # 093

[Joe 1320]

The left side of the transmission extension housing. Are you getting any codes? usually failure is indicated by a code...... that's why I suggest putting a scanner on it and checking what the computer sees while the needle jumps.

[Eric 97LT4SS]

No Codes, but have never had the scanner hooked up when the needle jumps because it is so random...maybe only 3 times this summer.

Thanks,
Eric

[tarsys]

Same problem

I am having the same problem with my 1991 formula firebird. I have already put a new speed sensor and it still did not help. Any other ideas?

[97LT1Z28]

I used to have an '84 Trans Am that did the same thing and we traced the problem back to being an electrical short and fixed it. Do you have any aftermarket stereo equipment that may be causing a short?

[Flash 97 WS/6]

Check for a ground strap problem

I don't know if anyone is still fighting with this problem? I had the exact same behavior a few years back after my supercharger install... finally tracked it down to the fact that I had not re-attached the copper ground strap from the frame to the drivers side head (I think that's where it was). If a strap has broken or corroded to death, that might cause some guage weirdness like that. Someone else might know off the top of their head where the ground straps are supposed to be? I am fairly sure there are others in there also.