Hey scotty my dad's 93 toyota corolla has a pretty bad vibration at idle and his speedometer only goes up to 35 then drops down but he would be doing like 50. How would I go about fixing these? Thanks.

try a new speedometer cable if it has one, if not, try a new speed sensor on the transmission. Vibration is often broken motor mounts you can check for cracks by jacking up the engine, or a dirty throttle that this can fix https://www.youtube.com/watch?v=NWCKvU2FmDc