1993 Coupe Speedometer Mind of its own
My 1993 LS Coupe is only used in no snow months in Maine. When I took it out this spring the speedometer was reading way low but then got better. Shortly later went bad again. I assumed it was VSS so I replaced it. No change. It is currently very predictable but way off. Using a GPS to measure I found the gauge reads 20 at 35 MPH, 30 at 40 MPH, is correct at 45 or so then goes the other way so it reads 80 when going 60. The Acura service manual shows a continuity test checklist if it's not working but I can't find anything about incorrect readings. Before I go and replace the speedometer and circuit board, is there something I'm missing.
Thank you in advance.