hi im new on this forum and i live in finland so sorry about my english.

i buy yesterday a miata na -92 1.6 and it's original and today it start f**k my brain.
the problen is when it's on idle about 850rpm tacho show 0rpm but if i push the gas it jump and start work... and when i loose the gas pedal tacho goes back to 0rpm. yesterday it works just fine. PLEASE HELP

here is link to video but it's not my but same problem

 

Sounds like the igniter may be going bad. Ive killed one so that it wouldn't drive the tach, but still fired the coils. You can put a scope on its output to see what kind of signal the tach is getting. Its also possible the tach is just going bad, but not as likely.