I have an 86 z31 with the same problem. Only its the tach that doesn't work. When the gas is pressed all the tach lights shoot up, and when the gas is depressed all the lights come down. So the lights work, just not the way they should. Should I take apart the dash and check the solders? Please help. Thanks.

 

I'm confused. Same problem as what?

So you push the gas pedal to the floor and start accelerating and the bars all shoot up.
You let go of the gas and stop accelerating and the bars go to the bottom.
Is this what you're saying?

That sounds normal to me.