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Driving home last night and this happened.

Anyone care to share their input to why this has happened?

Rocker cover gasket has a leak
Spark plugs are 25,000kms old

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Yikes!! Maybe a crack in the casing and a massive short to the rocker cover??

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Taliban?

Loose spark plug? Compression pressure got past the seal? Substantial energy caused this, there is not enough energy in a spark to cause it.

Red_Bullet wrote:Taliban?

Loose spark plug? Compression pressure got past the seal? Substantial energy caused this, there is not enough energy in a spark to cause it.

(Ding ding ding).

Correct from what I discovered. All plugs were loose, despite following the 'Hand tight then 1/4 turn' method.

The thing that concerns me now is the electrode from plug #4 is missing. Need an inspection camera to assess for damage.

Other than that, bought new plugs, heading over to Mania today for a new rocker cover gasket then a used set of COPs tomorrow.

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What brand plugs were they? I have read that Bosch plugs have a nasty habit of dropping electrodes. I swapped all my Bosch plugs out for NGK.

MX-5 torque settings link:

http://sandiegomiataclub.org/miata_tech/na/na_torque_specs.html

Red_Bullet wrote:Taliban?

Loose spark plug? Compression pressure got past the seal? Substantial energy caused this, there is not enough energy in a spark to cause it.

Well done RB, Top of the class for diagnosis. I would never have come up with that.

GR124 wrote:

Red_Bullet wrote:Taliban?

Loose spark plug? Compression pressure got past the seal? Substantial energy caused this, there is not enough energy in a spark to cause it.

Well done RB, Top of the class for diagnosis. I would never have come up with that.

Very clever, wasn't it?

Never offer beer to a retired elevator industry tech support man, especially on a Friday.

Now that it's been mentioned, it's pretty obvious too that there's a lot of carbon and crap that's been blown out of #4 too.

Evidence my dear Watson.

hks_kansei wrote:Now that it's been mentioned, it's pretty obvious too that there's a lot of carbon and crap that's been blown out of #4 too.

Nah, just oil from the rocker cover gasket.

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Red_Bullet wrote:What brand plugs were they? I have read that Bosch plugs have a nasty habit of dropping electrodes. I swapped all my Bosch plugs out for NGK.

MX-5 torque settings link:

http://sandiegomiataclub.org/miata_tech/na/na_torque_specs.html

NGK BKR5E-11, I believe.

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Red_Bullet wrote:Never offer beer to a retired elevator industry tech support man, especially on a Friday.

If you're retired then you can have a beer anytime you like.

Looking at the photos again it seems that the coil itself is not damaged, just all the bits that connect it to the #4 spark plug. It follows that you may not have to replace the coil. Instead you could just get the connecting pieces from another forum member whose coil has failed. Taking that further I think some creative work with a tube of silicone or RTV and some duct tape could put everything together again well enough for it to work until a replacement part arrives. At least that's what I would try.

kiezon wrote:All plugs were loose, despite following the 'Hand tight then 1/4 turn' method.

Were the plugs new? If so, a 1/4 turn wouldn't initially compress the gasket washer enough to properly torque the plugs. On the side of the box for a new NGK BKR6E-11, it shows 1/2 to 2/3 turns.
For 14mm flat gasket seat plugs in aluminium heads, NGK say torque to 18 - 21.6 lbft