bouncing tachometer

My tachometer bounces around while i'm driving. It mostly occurs through 1000-2500 rmp. It's even quit working completely a few times but not for long. Also, it sticks at around 4500 rmp so i cant tell when i'm approaching redline. The problem seems to get worse in cold weather and on a cold engine. I think it has something to do with wiring and not the instrument cluster. I reset the engine control management and checked the connection into the tach and the ecm. It might be where the wiring connects into the distributor but I'm not sure what color the wire is and where it connects (distributor?). Any help is appreciated. thanks.

maybe the idle control valve does it come close to stalling when u come to a full stop?

no, the car runs fine, its just the tach. the rpm it reads doesn't match the engine speed at all.

pull your gauges out and change the tach. i replaced my tach from one i got from the junk yard and it worked fine after that.