I have a 93 fd and the sppedometerl moves when accelerate in neutral. I recently cleaned up some wires and must have done something... It's driving me crazy

 

Is this supposed to be connected to something?

Is this supposed to be connected to something?

Random plug not plugged in?

Theres a relay between the yellow and black wire. I think this is what I disconnected but I'm pretty sure it wasnt hooked up to anything.

 

I have the same problem. Speedo works just like rev meter when car is not moving. I have no idea, what could be a point...

 

I had an issue similar to that when I had created a common ground between my wideband and one of the stock ECU ground wires

 

That's the point. I had removed my wideband some time ago and plugged it again. Probably I connected something wrong (...) Thanks!

 

I have the same problem. I swapped in a used speedo since my odo did not work and this happends. When I put the old one back in it does not happen, so I think it has to do with the speedo itself. It may be getting "noise" from the tach until an actual speed signal is detected.