I have a cheap AutoGage 5" tach that I use for the shiftlight that comes with it. Thing is, whenever the car's idling, the tach goes nuts. It randomly jumps from the idle RPM to about 4000 rpm in quick flicks, over and over again. It never does this when the car's being given any throttle whatsoever, which is what makes it so weird

Anyone solve this before?

 

where do u have the tach wired in at at the dizzy or ecu

 

He has it wired at the distributor

 

try wiring it in at the ecu

 

I would check your ground. Mine fluctuated when it wasn't grounded right.

 

I had it wired at the ECU and changed it when it started doing this, so I've had it both ways.

I'll check the ground tonight if I can get the frickin' car running

 

Sounds like your ignitor is about to die.

 

Brand new distributor and the stock tach is unaffected