Common problem. Had it on my Legend and assume it applies to other Acura models. You have a bad speed sensor. The part cost about $125 from dealer and about $86 on ebay.
The electronic chip inside is the sensor is going bad and needs to be replaced.
What you need.
1991 - 1995 ACURA LEGEND SPEED SENSOR REPAIR KIT NEW OE
Acura Part Number 06560-PY3-000
The instructions are included inside the kit.
Tips: Remove the one bolt holding the speed sensor on the differental or tranny. Have a towel handy to put inside the hole so you dont loose alot of fluid. Make sure to unplug the speed sensor and mark the placement of it and the gear placement with a permanet marker, SO it goes back in precisely the way it came out.
Do not get oil on the electronics; use the new seals provided, and make sure they gasket seals.