what would cause my tach needle to bounce

[80convertible]

Last year by car started running rough and I notice that my tach needle bounces a little...not much but not a smooth idle. I had not done anything to the engine, so I'm not sure what is causing this. My spark plugs, wires, distributor cap and rotor, air filter all have less than 3,000 miles on them. I know its not the tach filter because I've never had a tach filter on the car in the 5 years of ownership. This problem just started last fall. I belive my distributor is old. Could the distributor be failing and causing some kind of ignition problem which would cause the tach needle to fluctuate? Could this be related to a timing issue? Any suggestions are greatly appreciated.

 

[blasterfdc]

is the tach bouncing or is the RPM's of the motor changing? If the motor RPM is remaining stable but the tach still bounces the cable probably needs lubricated or is going bad.. I would start there.

 

[KANE]

The tach is electronic, so look for a bad ground on either the distributor (the one that says TACH) itself or in the dash itself. There is a small curcuit board on the back of the tach that could be bad. After that, it might be the printed curcuit board- but I doubt that.

 

[Scooter76]

Mine does the same thing. I think it is probobly the circuit board.

 

[Ludigdrums]

I notice a slight change in the Tach when I signal or use any electrical device actually. I think that's normal!?

- Jeremy

 

[wishuwerehere82]

You might want to check the connector that plugs into the TACH output on the distributor cap. That's your first signal source for the tach. The wires may be frayed.

 

[Yoda]

I notice a slight change in the Tach when I signal or use any electrical device actually. I think that's normal!?

- Jeremy

- Jeremy,

It sounds to me like you have a bad connection or bad ground connection somewhere in your dash or tach circuit. You shouldn't notice any fluctuation when your turn signals flash.. I agree with what everyone else said about the bouncing tach, esp. in the newer electronic type.