i have a 90 ex accord. while driving the tach will go from 2200rpms and jump to 4200 rpms and it wont budge from there unless i go over 4200 rpms or if i go under 2200 rpms. Any ideas?

 

Tach problems can be caused by bad spark plugs, ignition wires, coil, or ignitor. If you're having any drivability issues, ignition system needs careful inspection and repair.

If ignition system is working fine and tach misbehaves, the tach movement or instrument panel electronics are the problem. You can pull and replace w/ used or have yours repaired (google for repair sources).

good luck