funky tach readings
 

i adjusted the idle on the TB and i had it at about 700 and it after a couple of starts it came down to the picture bellow. occasionally the tach will jump around in about 300-500rpm increments unprovoked, some days it will read 4k @ 65, other days 3.5k. wiring, tach, cas, TB? i don't think it has anything to do with the clutch because i did the full throttle at 40 in fifth test with no slipping (referring to the 3.5k 4k variation.) i'm pretty sure the o-ring on the cas is fried so i'm going to start by replacing it.

i just wanted to know if this was even possible for miata engines to idle stably at this actual rpm, because it definitely wasn't complaining (i increased the idle after i saw this):

what computer are you using? is the battery and coil good?

computer? i have a stock ecu, i haven't checked the battery or the coil, those are probably good places to start. i plan on upgrading to cops, so that should eliminate the problem if it is coil related. i'll check the battery when i get i chance, but come to think of it those two things make a lot more sense.

:facepalm:
Grounds grounds grounds.
This is a really common problem.

Check the ground behind the head under the heater core, and on front of the block by the throttle body.

this makes even more sense. i'll check it out when i get a chance.