1987 RX7 FC, non turbo, automatic...

When you go over about 50... the speedometer just isn't right... It says you are going about 12- 15 mph faster then you actually are. Also the "warning lights" and clock at the top of the dashboard only work when they want to. lol... The hatch open and door open lights always work though.
What's going on? How do I go about fixing this?

FYI: The rims are 13"... I replaced the tires last week, but they haven't been changed at all to my knowledge.

 

The problem is your rim/tire size. Stock rims for your model are 14x5.5 with 185/70/14. Your wheels are spinning more and therefore reading faster. Only good way to fix this is to obviously get stock rims/tires.

Also, all this information is in the FAQ at the top of the 2nd gen section.

 

Also, do you have the original 3rd member. I believe a S4 Auto is 3.9, while someone might have swapped in a 4.1 for better performance. Just need to get the correct speedo gear into the tranny.

 

Why are there 13"'s on your car?

 

I have no idea. lol. The car was a one owner car and they were like an old couple. So I have no idea why they would change the rims... if they even did. lol