in my 89 Iroc, my tach will just peg at like 5600 and wont move for a few days, then if i get into it, the tach will come back down and work just fine. Then it will just flip up and stop working, although it doesnt affect the performce of the engine, i would just like to have it there and working.

 

ttt

 

My tach was going crazy for a while, then I started getting a trouble code for the EST... replaced ignition module, all problems solved. Maybe yours is going?

 

check the plug or something...

 

Make sure you've got a good body ground from the engine block.

 

I would just check and make sure that all cables are tightly in place and lubed up. My 83 Z used to do it, but it only seemed to do it when it was cold out.

 

checked body gorunds, now i just need to pull the cluster back out, and pull the tach and check the actual board for breaks in it.

Thanks for the suggestions guys!:hail:

 

Also check the wire connecting to the coil and the ignition module. I had a similar problem and found out the problem was that one wires was cut and the actual wire was exposed. Must have been arcing to something but after changing it out, my tach never acted up again.

 

do you remeber wich color wire it was that was rubbed through?

 

It was the set that ran from the Module to the Coil. I want to say they were red and white. The white one was exposed. Hope that helps.