So I noticed recently that my tach needle will twitch and bounce back and forth a couple hundred to thousand rpm sometimes when I let off throttle. However when I am appling any throttle pressure or in neutral it does not do this. The only thing I could think of that might be causing this is a bad cam position sensor? but not totally sure sense I haven't messed with it.

I'm wondering if this is a common problem with miata's ?? or if anyone has heard of this happening? Thanks

 

ignitor is dieng on you prob get a new one and your prob will eb fixed. Since your ignitor is built into your coils this means you will need some new coils.

 

will a coil pack off a 1.6 work? or only off of 1.8l NA's? Is it common for the coil packs to start f***ing up? I mean the it still accelerates and drives fine aside from my crappy bottom end tune

 

A 1.6 unit will not work as the **** is totally different.
If you are lucky the tach signal is just going out. Failures arent common but not unheard of, just like any coil given enough time/heat/vibrtion **** will start going down hill. If you have experiened no real preformance loss then i wouldnt worry about it but, and erratic tash signal points towards a ignitor going out 9-10 times. The other 1-10 its the ground under your throttle body try cleaning that off before you go out and buy abunch of ****.