I have started having some problems with my tach and they seem to be getting more frequent. At first it only did it when in was really wet outside but now it does it anytime it wants. Basically it is not reading the correct engine speed. Sometimes it works great and other times It is all over the place. I noticed at a stoplight today that the tach read zero while my engine just hummed a nice idle. And then when I pulled away from the light my tach jumped up to 2000 and climbed fast and high up to around 5000 about the time I shifted. My shift couldnt have been higher than 3500.

Any ideas to fix this one?

 

Is this a factory tach, or an aftermarket..?

 

If its factory, clean your coil/igniter to body ground and your battery to body ground.

 

It's the factory tach

 

This happened too me mabey a mounth ago, pull your distibuter cap, and clean the sensor that the tach is run off, and it should be fine

 

Well guys I have tried everything you suggested. I noticed a real improvement right after I cleaned the coil to body ground.

Could this have something to do with the alternator ground?