If you have a tough one in an aluminum head, replace the rest of the plugs and disconnect the injector for the bad cylinder. Start the engine and get it hot enough to get the thermostat to open (upper hose gets hot and seals the cooling cap valve. Shut it off and as soon as you can stand the heat, get on that plug and work it out gingerly.The engine will run ruff, especially if it's a 4 cyl but it won't hurt the motor. That cyl becomes a air compressor.
If you snapped the plug off in the head, the head will likely have to come off to get it out if an EZ out won't tap into the insulator cavity.
take the head off and take it to a machine shop
Not easily. Avoiding damage to cyl head is hardest part. Cast iron heads not as bad as aluminium types.
If socket will not remove plug after soaking outer section overnight in wd40..? We may need to risk stripping threads by using brute force. This would mean head off and lots of expense.
Don't heat engine as in case of aluminium head it expands more than plugs so will grip tighter.
If we decide to try removing ceramic to allow drilling down side of plug reducing pressure on threads etc be very careful as easy to do more damage.
Cutting into threads for example. Once plug is removed do clean cyl combustion chamber from detritus etc.
Where did it break?
