Pumped

My tach on ignition II with the car off, my tach needle fluxuates.. it jumps around from 0 1k 1.5k etc...

so naturally when the cars on, it jumps around when i'm driving, but it doesn't affect the drivability so say i'm idleing 1k , itll read as 3k, but it it still sounds and feels like it idleing at 1k

i've tried adding ground wires, but nothing.. i think it help a lil, not sure

any sugestions?

oh it'll act normal after say i drive for a while then turn off the ignition and start it back up again.

Pumped

anyone?