95 hatch with b18c swap.
Problem with tach is at idle the tach sets at zero. When I rev or drive the tach moves but is incorrect. The engine used to rev to 8300rpm now the tach shows around 8000rpm when the limiter kicks in. I'm sure the engine is reving to the correct rpm just the tach is off. I started noticing the tach would read low at idle sometimes. Now at idle it sets at zero. I removed the distributor cap, everything looks clean. I replaced the dist. rotor and plug wires. They where old and showing signs of wear. This didn't help. I unplugged the 2 wire harnesses located behind the distributor they look clean. I sprays some WD-40 in the harness. No difference. Any ideas? I did search.

 

At idle does the needle move, or does it stayin the same place as when the car is off?

 

It just lays there. I read if the needle jumps it means the coil is going bad.Correct?