1987 Pontiac Sunbird Speedometer problem

I have just recently noticed that the mileage gage does not climb when the speedometer is not moving when I am driving, and when the car is not moving, but the speedometer is jumping around the mileage will count up as if i'm driving.
Any input is greatly appreciated!

Hello there. Our car does the same thing. About ten minutes for us. We just set the miles counter to 0 every time we put gas in and track the miles. We have had mechanics look at it and to no avail can they see why and how to fix it.

If your others gauges aren't working it's probably your instrument cluster. I had the same happen to my car(91 sunbird), and replacing the cluster fixed the problem. I have a friend who's a mechanic and he has seen it three other times on these cars.

The only problem is that the only way you can fix it yourself is going to a scrap yard and getting one, because if you take it to the shop, they'll have to send it to the dealer(The cluster is sealed). The dealer won't accept it from people(like you and me, they are afraid of people messing with the mileage), only repair shops, and they will charge you an arm and a leg( I was quoted at $400). Now, I bought mine from the salvage yard for $25, easy choice for me.