I have an '84 with the 2.5 L I4. The Tach stopped working and I was wondering if anyone might know where I should check. I am assuming a cable came loose or something, but am not entirely sure.
Most likely you have a bad tach filter - it's a aluminum cylinder about 5/8" in diameter and 7/8" long and it's usually mounted to the ignition coil bracket. If you can find one in the boneyard it might be OK - this part is no longer available from GM. Rodney Dickman also has a custom made replacement for this part - you can find it here:
Well, I have dash work to do anyway. So while I am in there I will look into the Corrosion thing on the guages. I have had my Fiero for a week and 1/2 now and have already ordered 1 part from Rodney Dickman's (fast service) and will be ordering another in the next day or two. I wish I knew all that I needed so I can just order it all......like maybe a whole new rebuilt Fiero....LOL....