Does the engine run ok? If it drives normally but the tach is screwy then take it out and drive the piss out of it and the tach should go back to normal.

okay that is what happened..
 

I changed the coil, I got coil packs from amazon, turn out the packs has one side bad coils, so the car was missfireing badlly but with two cylenders and the misfire the tach workd yaaaaaaaaaaaaa???????? then i ordered a new coil to fix the misfire and installed it... the tach stop working again???? i checked all the grounds all good and clean...i so ****up