Originally posted by TourDeForce:
I immediately had that same question & here is how it was explained to me. If the plug wire or coil is going bad, it causes a mis-fire. The ECU then kicks up the voltage to the suspect cylinder to try & force spark through the plug & avoid damage to the engine.

As the voltage spikes, this raises heat within the plug causing the core to expand & burst the insulator.

So, you can have good plugs in the engine, but if the wires or coil create too much resistance, the ECU still must raise the voltage to get adequate spark to that plug and poof, the plugs burst from the excess heat that is generated from an over-voltage condition.





No offence, but where are you getting this stuff?



The coil voltage is not adjustable. Peak spark voltage available depends upon coil winding ratio. If dwell (coil saturation) is not sufficient, output voltage is reduced. Final spark voltage reached depends upon spark plug gap, the compressed mixture's dielectric value, or leakage which drains energy causing a spark somewhere besides the plug's tip. Ignition module and wiring problems can reduce spark voltage. So can shorted secondary windings on the coil. Increased plug wire resistance reduces spark current. The spark only contains a few watts of power. This will not blow anything up.



As most books will tell you, shattered plug insulators are usually caused by detonation. Crossfire between leaky plug wires can cause occasional detonation. Detonation causes drastically increased pressures within the cylinder and can damage plug tips and ceramic insulators.

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