Overheating coil

Hi
I have a problem with the coil nearest the bulkhead overheating
It overheated so bad it split and failed. Thought it was a faulty coil, but replaced its done it again.
any ideas what would course this.
Engine isn't overheating and was running great till it started missing and running rough. thought it was the crank sensor and replaced it but then while running the engine after fitting it the coil failed.
Jimny is a 2002 hardtop with the M13A
thanks

Tried to find a circuit diagram of the system in order to offer help but did not have much luck with that, so just going with some initial thoughts.
What condition are the plugs in and are they standard?
As spark plugs wear down, the gap in which each spark plug is fired is widened, meaning the coil needs to provide a higher voltage in order to bridge the gap. This additional strain on the ignition coil may cause overheating and eventually failure.
Also check your earth points on the engine. Have seen similar on an MX5 that was caused by a loose / missing earth on the engine.

Is this a replacement engine (M13A in 2002) and if so when was it done ? Only asking as I don't know when they started to fit M13A and the possibility of incompatible ECUs - if there is such a thing. Over to the experts.

Sorry can't offer much more help.

Mike

I'd look for something someones added to the ignitor circuit....very odd!

The circuit diagram shows that the power switching device (npn transistor) is integrated into the coil. It would be interesting to see if any signal difference exists between the Green/white and Green Yellow firing signals from item 11, but you are going to need an oscilloscope to be sure. They should be the same signal levels to ensure both coils are turned off/ on the same, I suppose it's possible one is not turning off fully due to a fault in the pnp driver circuit in item 11, hence no cooling period. I would have expected reduced performance (missing engine) on the coil pack if this was the case, but as with everything, not always a certainty.
That said you need a good earth on the coil pack and spark plugs within tolerance to avoid damage, and as Keithy said look for any previous owner modifications. Start with the simple things.

One thing's for sure, you are going to need a replacement coil pack! As you need to fit it you could monitor it's temperature in relation to the other coil pack, eBay sell cheap none contact thermometers. Example

ebay.us/swaBlb

It's not going to tell you what's wrong, but it will give early indication that you still have a problem rather than waiting for it to melt.

Good luck
Mike