Tach stuck at 4 grand??
 

92 5.0L... what could cause this.... any fix... when rev'd beyond 4000 it will pick it up and carry on to what you rev to.. then back to 4000

get a new tach either aftermarket or replace the one in your dash with a used one. you could try fixing it but it sounds like its screwed

was it a 4 banger before it was a v8 cause mine does the same thing it goes to 4000 then back to 1000 and so on and so on.