It sounds like the compensation brd in the dash right at the temperture and fuel gauge. Was it always this way or did it just start acting up? this comp. brd works both the fuel and temperture gauges. My Temp. gauge was all over the place. I think it was Don who had photos that he sent me on what the heck it looks like. a little time and a little solder and mine works perfect now.

If you are willing to take the dash apart click on the envelope next to my name so you can e-mail me direct. I will try to give you a blow by blow.