I agree with mountainbike
By 1993, the oxygen sensor light had been gone for several years
A timing belt can certainly skip a tooth and make motor run bad. Buddy had civic with 100k miles and old belt.
The only timing belts I’ve heard of slipping are ones that weren’t installed correctly. Belts don’t stretch like chains do. They’ll break before they stretch.
On my Toyota Celica’s W50 tranny, the gear ratio of fourth gear is 1:1. Fifth gear is an overdrive.
There’s no harm in driving in 4th.
Ever heard of shedding a tooth,Mike?Things can slip on the sprockets too.