Spark plug gap closing up in motor

I know it's not an LS1 specific question and that this is an LS forum but thought here would be a good place to ask...

My brother has an FG xr6 turbo, 6sp auto and has had 2 spark plugs close up completely while in the motor.
The car has just over 100,000kms.

BACKGROUND:

The car was involved in a front end accident which broke the plastic intercooler piping. The car was driven with the broken piping for a few seconds to get the car out of the flow of traffic. I "think" the car did stall during this time.
There was also a car battery in the boot which leaked acid through the boot so panel shop replaced boot floor etc.
Car was repaired by panel shop and within minutes of getting the car back it began misfiring.

The throttle body was then cleaned, oil, oil filter, air filter and fuel filter replaced which didn't help. So we changed the plugs which fixed the bad misfire. 3 weeks later the misfire returned and the coilpacks were changed which didn't help.
The car threw a code "misfire cyl #2" so I pulled that plug and the gap was completely closed ie: ground strap pushed hard up against electrode.
I replaced that plug which has again fixed the misfire (but for how long).

We then checked the original Ford plugs that had been replaced after problem first occurred and one of them was completely closed too, so the original Ford plug and the replacement have both closed up in the motor.
Mechanic checked #2 cylinder with a borescope and said there was carbon buildup around the edge of the piston that he considered to be a little excessive considering the kms of the motor. But other than that everything else looked normal and he doesn't believe the buildup would be causing the plug to close up.

Has anyone here experienced this type of issue before and is there a common cause??

Thankyou.

I would double check it isn't fouling up and closing the gap by hitting/touching piston to plug. Probably odd chance but won't hurt.

Never ever heard of an electrode gap closing! Heat of combustion over time can only open the gap as it expands or electrodes pits etc.
Are the replacement plugs the correct reach?

Plugs are the correct type and length etc.
It happened to the original Ford plug that had been in for years too.

When the Mechanic Bore scoped it was there any sign of the piston hitting the plug?

There's no other way for it to be closing the gap down in normal operation.

Any other noises or signs of distress from the engine?

Blowby or pushing the dipstick out under power?

Quote:

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Originally Posted by IJ.

When the Mechanic Bore scoped it was there any sign of the piston hitting the plug?

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Would think that would be the first thing they looked for.

Any further information?

Quote:

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Originally Posted by zorro

Would think that would be the first thing they looked for.

Any further information?

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It's not always evident if the engine is heavily carboned up Ash.

I was more thinking evidence in the carbon build up if any on top of the piston that would indicate contact.

Just My 2c would do a comp test on the offending pot both Hot & Cold then compare to Veh. spec.

Mechanic does not believe the piston is contacting.
Car is running ok with the new plug in there now, my brother does think it still feels a little off but can't explain how...lol.
Mechanic wants him to keep driving with the new plug and if it happens again check & service injectors.

do the electrodes on the standard plug extend out of the plug body if they do try a plug (with the same reach) with a shorter electrode, just a thought, to see if it closes up, let us know as i am a mechanic for 35 years and never had this happen good luck.

Worst case is head off for close up looksy, no biggy with the ford sixpack.

Quote:

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Originally Posted by Micks

Worst case is head off for close up looksy, no biggy with the ford sixpack.

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Was going to say easy job to pull head and have a look.

doesn't detonation cause the plug gap to close?

Quote:

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Originally Posted by Black VU SS ute

doesn't detonation cause the plug gap to close?

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Been thinking..........and i am probably way off here...........What about boosting will that maybe cause a problem? Overboosting? my 2c worth!