A little background: I live in Australia and am 17. I have a 1985 Fiero gt as a weekend car and recently I have had enough money to start restoring it.
I recently replaced the coil and ever since the tacho has been playing up reading about 1000 to 1500 RPM higher than its actually idling. The coil is a Bosch coil MEC717.
is there anything that i could be damaging from this? Have I done something wrong? I'm not sure as i don't know too much about Fiero's.

Maybe you need a new tach filter.

Hi Cruza,

I'm from Australia too. I bought my GT when I was 17 and have owned it now for nearly 5 years and have been driving it daily. They're exciting cars to own, so I hope you enjoy yours too.

As TopNotch suggested. The tach filter might be a good place to start, since they're inexpensive to replace. Rodney Dickman sells those (www.rodneydickman.com).

Was the tach reading correctly before you replaced the coil?

quote Originally posted by James_GT: Hi Cruza, I'm from Australia too. I bought my GT when I was 17 and have owned it now for nearly 5 years and have been driving it daily. They're exciting cars to own, so I hope you enjoy yours too. As TopNotch suggested. The tach filter might be a good place to start, since they're inexpensive to replace. Rodney Dickman sells those (www.rodneydickman.com). Was the tach reading correctly before you replaced the coil?

Yes, the tach was reading correctly before I replaced the coil. the car sat around for about 4-5 years before I bought it so not everything works well. when I bought it, it wasn't idling properly, so I figured to start with the coil.

Australasian Fiero owners unite!

Mine's doing the same thing on the stock coil, I've been meaning to suss out a new tach filter for a while but just haven't gotten around to it.

I just picked up an '88 Formula which had no instrument cluster. I've tried three different clusters, and the tach only reads correctly on one of them. One of the other tachs reads more than double and the other one reads nothing.

I did some research and I suspect it's the capacitor for the tachs which has failed. Read about this Here.

quote Originally posted by Lambykin:

You'd be correct, Fieros aren't the only one plagued with this. G-Bodies (Malibu, Monte Carlo, etc.) and F-Bodies (Camaro/Firebird) from the same era have had the same issues.