Freeing Stuck NC Miata Spark Plugs

I can’t believe I’m blogging about this. Spark plugs. Don’t they barely deserve 3 words typed about them ever? But here I am.

Because the Stormtrooper’s plugs were damn near welded to the head and required some heroics. I thought I’d blog about said heroics and hopefully help out some other folks.

Stone cold. Ready to work.

Back story – I bought some new plugs for Stormy. Nothing special. I got a set of NGK “laser” Iridium stock plugs (ILTR6A-13G or NGK 3789). The plugs apparently get changed about every 50k on NC Miatas. At 156k, Stormy was due.

I grabbed my trusty 3/8″ ratchet, extension, and spark plug socket and attacked plug #1.

and… nothing. I grunted and groaned. Nothing. That plug was IN there.

I grabbed a breaker bar and applied that to the poor spark plug. And I strained and grunted again. And finally…. CRINK CRINK CRINK.

Just the worst sound and feeling ever to have come out of an aluminum cylinder head. It was the sound of threads coming out of the head. I stopped right there and regrouped.

This post is about the regrouping.

The Big Guns

A bit of research revealed this is pretty common with Ford trucks. The plugs get welded to the head and break apart when you try to remove them. Owners need to use a special technique to get them out.

1: Work on a stone cold engine. This is very important. Park the car and then work on it wherever you parked it the next morning. Don’t move or start it. You have a better chance of success with a cold engine.

2: Carb cleaner + penetrating oil will help. Note the cans I used above. They are really way overkill for this. Like bringing a bazooka to a shooting gallery. But I didn’t have any carb cleaner on hand, so MCCC had to do.

Soaking in it.

Spray the carb cleaning in each plug well. You don’t need a lot, but you want to soak the threads around each plug.

Then add some penetrating oil to help lubricate the threads. Don’t use WD-40. Use a silicone oil or something like that. I’m a huge fan of PB Blaster. It’s an almost magical fluid.

Let the fluid combo sit for a couple minutes. You really don’t need to wait long, just a bit to let things start to work.

Break each plug free.

3: Break each plug free, then re-tighten. It’s nerve wracking to break the plugs free, but it has to be done. No time like the present.

Once things are slightly loose, just re-tighten and let sit for another few minutes. You’re trying to get a bit of fluid down the threads. You can even go back and forth breaking free and re-tightening for really stubborn plugs.

Note, you do not need to fully torque each plug back in place. Just a bit of tightening is needed.

Sweet success.

4: Remove the plugs. After an initial struggle on each plug, they all came free easily. Maybe the first turn was hard after performing the above steps, but all following turns were very very easy.

And holy crap did it feel good getting those plugs out without destroying the head. Such relief. OMG.

Old plugs

I was pleased to not find FoMoCo plugs in the engine. Those would have been the factory original plugs. The ones I found were the exact ones I was installing, just stamped with MAZDA. So someone changed these between 50 and 100k miles.

Yay for basic maintenance!

The plugs looked pretty good. No red flags that I could see. Correct heat range plugs on a stock engine.

New plugs ready to go in.

I gave each plug a bit of anti-seize compound before installing. This seems to be a bit controversial now days. I researched this topic and found all manner of opinions on modern spark plugs and anti-seize.

Some folks claimed modern plugs don’t need any compound at all. Others liked nickle based anti-seize. The vast majority seemed to like the classic copper anti-seize.

I’m not here to suggest anyone out there do one thing or another. I used the copper stuff. I’ve done that with every plug I’ve ever changed for the past 20+ years and never had a problem removing a spark plug. I crossed my fingers and greased up the Stormtrooper plugs.

I torqued to 8-10 ft/lbs, which is factory spec. I used my 1/4″ drive in/lb wrench to do it. It’s such a cute torque wrench. I should have snapped a pic.

And that’s it. Way more than I ever expected to type about spark plugs IN MY LIFE.