Ive noticed that every once in a while my tach will all of a sudden shoot up 4k rpm from where it is for no apparent reason really quickly, and just as quickly come back down. Has anyone ever seen this before? Is it a major problem? The engine itself isnt revving (as far as i can tell, but it changes rpms faster than i think it would be impossible anyhow).

Any ideas?

 

probably just need to clean up the solder joints on the back of the tach. I had a issue with my tach boucing around but then the car would also suddenly stall out, turned out to be a timing issue and bad wiring on trailing coil.

 

There is a fix which in pdf form from one of the members
I can email it to you if you give me your email
It consists of resoldering the joints and changing the capacitors
But it is quite a minute job