In every vehicle with engine number B16A2 producer installed great long working Honda bulbs. The only base type for Civic reverse lights is BA15S and no other. Of course, standard voltage of 12 V is used and power must stay near 21 W. Obviously it’s not only 1998 model vehicles with engine of 1.6 liters to have reverse lamp working right. Every car on the road including Honda Civic must have backup lights working. Before driving Honda Civic 1.6 make sure the backup lamp works properly.
It’s up to professionals to repair 1991 Honda Civic electrical system if it doesn’t work properly. Make sure that for B16A2 model number car with 1.6 motor you bought exactly 21 W light bulb. The replacement of any lamp in Civic 1.6 produced by Honda may be a challenge. First thing is to buy only 12 V type of bulb with base BA15S.