NC Miata Spark Plug Change

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While I’m waiting on the title to come in on the Miata, I figured I would check off some maintenance stuff of my To-Do list. First on the list is spark plugs. Since I’m doing it, I felt I might as well do a little tutorial, more for practicing my tutorial skills than anything else.


This is some pretty damn basic stuff, took me about 30 minutes with a coffee break included, and only requires basic hand tools. You’re gonna need:

  • ​ratchet
  • ​extension
  • 8mm socket
  • 12mm socket
  • 16mm spark plug socket
  • spark plugs
  • pick up magnet

That’s about it.

We’re gonna start by popping the coil cover off. It’s going to look like this when you pop the hood:

Just grab the little plastic cover on your right hand side and pop it up. It takes a little bit of effort, but not much. Once you get it popped off it will look like this:
Next, you’re gonna want to unplug the connector by pushing on the tab that faces up, and then remove the 8mm bolt holding the coil pack to the valve cover.
Once those are done, just lift the coil pack off the spark plug and set it aside.
You should see the spark plug down in the head.
Use the spark plug socket, extension, and ratchet to remove the spark plug, then use the magnetic pick up tool to retrieve the spark plug.
You should check the gap on your new plugs as a matter of course, but mine were fine out of the box and they generally are. Use the socket and extension to put the new spark plug in. Do not use the ratchet yet, make sure you get it smoothly threading in by hand before you use the ratchet to put any torque on it. You do not want to cross thread a spark plug. Torque them to spec, which I didn’t bother looking up because I just torque them until it stops turning then give it a few extra degrees to snug it down, but do as I say, not as I do and use a torque wrench.


Once you have the plug in, put the coil pack back on and screw it down, then plug it back in. Do the same thing on the next two cylinders to remove and replace the spark plugs. When you get to the rearmost cylinder, you will notice you have a strut tower bar all up in your way. Luckily, Mazda made it very easy to remove. Two 12mm bolts, one on each side, the middle piece on.

With the nuts removed, the strut tower bar will lift straight off without issue and you can do the last cylinder just like the first three. Once you have it done, double check to make sure all your coils are plugged back in and screwed back down and then pop the cover back on.