Well i just got my 87 GTA last weekend. i love the damn car. But the only thing irritating me right now, is the fact that my tach reads about half of what it should at any rpm aside from idle. When the car is sitting it read 800 and it fluctuates with the small misfire the car has. But when i accelerate the tach will onlly read about 1/2 of what it should. Example, At WOT the highest the tach goes is 3000. and i know for a fact that the car is revving higher then that. Any ideas as to what this may be?

 

Determineing how much difference there is may help. Try connecting a handheld diagnostic tach and comparing the two at various engine RPMs.