93 civic hatch wont go past 30mph??????

my buddy is expierencing problems with his 93 hatch.......when he hits 30mph the speedometer needle starts to bounce really bad and wont let him go past 30mph. car doesnt shake or jerk when it happens. anyone have any ideas what could be wrong? thanx

well how modified is his car. thats usually a good indication on where to start.

well how modified is his car. thats usually a good indication on where to start.

just a cold air intake and catback exhaust

i almost wonder if one of his main systems is going out specifically his dizzy. sounds like an issues i had when my dizzy went bad all 5 times. they either crap out or they go speratically only giving spark when they care. but really it was almost like a rev limiter. start there. test all major system if you can. do a compression check all that jazz make sure he doesnt have a dead hole either.