WE have a 90 accord,I believe that 90 to 93 are the same.Anyway,we had the same problem,we ended up replacing the speedometer sensor,that fixed it.It's located on the passenger side above the differential part of the trans.There is 2 bolts that hold it in,and one connecter.Be careful not to lose the little adapter inside,you'll need that when you put the new one on.Hope this helps.

 

Replaced the VSS and still no luck. The speedometer still doesn't work.
Also, it did something strange. i took it around the block, when I turned into the driveway the green"D4" on the dash (the gear indicator) was flashing off and on. I put it in park, the red "P" lit like normal but the "D4" still continued to flash... turned the car off and started it... no flashing of the "D4". Any thoughts?