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?

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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?

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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.

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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?

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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!

I think the Ops bro's mech. needs to get back to basics instead of changing things & properly diagnose the problem!! Is why I suggested a comp. test previously.
After all it is a 100k turboed cab!!

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Originally Posted by Micks

I think the Ops bro's mech. needs to get back to basics instead of changing things & properly diagnose the problem!! Is why I suggested a comp. test previously.
After all it is a 100k turboed cab!!

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The mechanic hasn't changed anything at all. He only checked the bore with a bore scope.

The car came back from the panel shop and was misfiring/very rough idle. My brother took it back to the panel shop where they said they didn't touch anything to do with any cooler piping or anything that could affect engine operation, only bodywork. But on the receipt it states new cooler pipes were fitted. They then suggested my brother take the car to their mechanic to be diagnosed and if the problem was due to something they had done they would pay for it. Their mechanic had the car for a while and then told my brother the coilpacks were gone.

My brother then bought new coilpacks and asked me to fit them, but when I went to fit them I realised the supplier sent the wrong type. So while I was there I changed the spark plugs and refit old coilpacks. The car ran fine with new plugs and old coilpacks.

I changed the oil, oil filter, fuel filter and air filter as they were all due. I cleaned the TB as my G6ET (same motor etc) had a rough idle when I bought it and cleaning the TB fixed this for me and my brothers TB was fairly dirty.
When the problem returned (3wks after changing plugs) my brother's friend changed the coilpacks, which did not fix the issue so my brother took the car to "his own" mechanic where they pulled the code for misfire in cyl #2.
I then removed #2 plug and found it was completely closed. We then checked his original Ford plugs that had been removed 3 wks earlier and one was closed shut, all others fine.

The mechanic then checked with a bore scope and said besides a little more carbon buildup around the outer of the piston everything else looked normal. He then suggested my brother keep driving the car and if the problem returns he would test the injectors and go from there.

I personally don't agree with driving it til the problem returns without knowing what's causing the plug to close up as my brother has little 'mechanical sympathy' and driving it with an unknown issue could end up very expensive...so was hoping someone here may have seen or experienced a similar situation before.

I'd almost bet my leftie that nothing will close the plug like that other than mechanical impact...

Could???? that one cylinder of had a hell of a lot of carbon vs the others, carbon would be hard enough to do it, and you wouldn't really see the thickness of carbon with the scope. Compression test?

the only time i have had the gap close on a plug is when parts of the ringland on the piston started breaking off.

I'd say some thing has gotten into the motor.

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Originally Posted by ***VX*R8***

The mechanic hasn't changed anything at all. He only checked the bore with a bore scope.

The car came back from the panel shop and was misfiring/very rough idle. My brother took it back to the panel shop where they said they didn't touch anything to do with any cooler piping or anything that could affect engine operation, only bodywork. But on the receipt it states new cooler pipes were fitted. They then suggested my brother take the car to their mechanic to be diagnosed and if the problem was due to something they had done they would pay for it. Their mechanic had the car for a while and then told my brother the coilpacks were gone.

My brother then bought new coilpacks and asked me to fit them, but when I went to fit them I realised the supplier sent the wrong type. So while I was there I changed the spark plugs and refit old coilpacks. The car ran fine with new plugs and old coilpacks.

I changed the oil, oil filter, fuel filter and air filter as they were all due. I cleaned the TB as my G6ET (same motor etc) had a rough idle when I bought it and cleaning the TB fixed this for me and my brothers TB was fairly dirty.
When the problem returned (3wks after changing plugs) my brother's friend changed the coilpacks, which did not fix the issue so my brother took the car to "his own" mechanic where they pulled the code for misfire in cyl #2.
I then removed #2 plug and found it was completely closed. We then checked his original Ford plugs that had been removed 3 wks earlier and one was closed shut, all others fine.

The mechanic then checked with a bore scope and said besides a little more carbon buildup around the outer of the piston everything else looked normal. He then suggested my brother keep driving the car and if the problem returns he would test the injectors and go from there.

I personally don't agree with driving it til the problem returns without knowing what's causing the plug to close up as my brother has little 'mechanical sympathy' and driving it with an unknown issue could end up very expensive...so was hoping someone here may have seen or experienced a similar situation before.

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No worries, obviously more diagnosis required. Hope he can sort it without too much expense.
As you said tell him not to flog it too hard until then!

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Originally Posted by seldo

I'd almost bet my leftie that nothing will close the plug like that other than mechanical impact...

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+1

Cheers

Steve

I've never heard of a plug closing up without contact of some sort.
You mention that the intercooler was replaced due to accident damage. Is it possible that some of the piping has somehow been ingested into no 2 cylinder & after a bit of rattling around, expelled out the exhaust ???

Check the turbo's turbine wheel. If something has gone through the engine and closed the gap on a plug I would be surprised if the turbo got off scott free.

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Originally Posted by Woodchukka

Check the turbo's turbine wheel. If something has gone through the engine and closed the gap on a plug I would be surprised if the turbo got off scott free.

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Good suggestion. I forgot about it being turbo'd...... damn new fangled devices !!

Sounds like the Jury's out best get Henry's head off pronto before it's goodnight mota!

A was mentioned above, I would be looking at the intercooling piping breaking and being injested that caused the damage.

Also check the earth strap for the battery, a poor earth connection could be causing your misfire too, it is possible that the two incidents are not related. (although doubtful)

My thought was that it sucked something in while cooler piping was broken hence the borescope. But the mechanic does not believe this is the case.

Also when changing plugs the first time we had the intake pipe off the turbo and the blades looked ok to me. Might be worth another closer look.

Oh well if all else fails wind the boost up :burnout::stick:

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Originally Posted by ***VX*R8***

Also when changing plugs the first time we had the intake pipe off the turbo and the blades looked ok to me. Might be worth another closer look.

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Check both sides. Intake and exhaust with snails removed. I have seen turbos with fins broken off hidden more inside the housings that look ok at a glance from just the intake or outlet of the snail.

Two popular reasons are...

1. Mechanical Contact: Anything that touches the electrode will move it to some degree. I've heard of many motors that had this issue and once fixed, the motor blew... Whether it was stretched rod bolts, broken piston skirts or bad bearings, something was allowing the piston to just touch the plug and close the gap. I've also heard of motors that had no issues once the plug was replaced and the belief was that some carbon had come loose and caught between the plug and the piston. This leaves no sign of the "touch" but is sufficient to close the gap. I've heard of some "tolerance" issues as well, where the plug length on some plugs was just enough to touch the piston, but only at max RPM. Finally on this one, there was one report that the ceramic centre of the plug can come loose and slip down onto the electrode.
   
2. Detonation: The theory here is that the shock wave and heat from detonation can close the gap. I find it a bit hard to believe, but given what I've heard some Toyota's do, I guess it could happen.

What I'd do is to look at the plugs and confirm the ceramic has not moved. Then I'd check the thread to see how much was exposed to the combustion chamber. There should be some soot one the start of the thread, but no further into the threads. If the threads have soot on them, then the plug may be protruding too far into the cylinder.

If the plugs turn out fine, then check the turbo as already suggested. It may never happen again and maybe nothing will happen, if so, go buy a lottery ticket....

Good call on the center electrode. Detonation might cause that to happen as well I suppose? A bit off topic but now you mention it I had a Honda Odyssey and it completely lost the center electrode on 2 plugs. Completely gone with no apparent damage to the piston or head.

This is the plug that was in for about 3 weeks.
http://i297.photobucket.com/albums/m...psf1a98b89.jpg

Try a double washer see if it still does it, have you had the tune checked.

Did the flash go off when you took that picture? It is just that the center electrode has a lighter patch on it. It is not a uniform colour like something has hit it. Plus in that picture the centre electrode look off centre.

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Originally Posted by Bling Bling

Try a double washer see if it still does it, have you had the tune checked.

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It's standard tune still.

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Originally Posted by Woodchukka

Did the flash go off when you took that picture? It is just that the center electrode has a lighter patch on it. It is not a uniform colour like something has hit it. Plus in that picture the centre electrode look off centre.

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That's not from the flash, the electrode is just very clean at that part, I'm guessing once the plug closed it got washed with unburnt fuel (??)...
The centre electrode has been hit by the ground strap which probably did push it off centre as it did damage it.

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Originally Posted by ***VX*R8***

The centre electrode has been hit by the ground strap which probably did push it off centre as it did damage it.

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Detonation wont cause that, definitely impact damage.

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Originally Posted by lmoengnr

Detonation wont cause that, definitely impact damage.

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If it was my engine I'd be pulling it out for a close look pronto, before you had a lot of smaller pieces to sweep-up...
It has either ingested something, (although to do it twice suggests that the foreign body is still there) or else there is something loose and about to part company with whatever it is supposed to be attached to (Piston crown, con-rod...)
Once upon a time back in the dark-ages I had a bit of miss with an oily plug and thought I'd give it a bit of a rev to clear its throat........Never found the rod or the side of the block.....:eek:

From my earlier post questions I'm thinking it's missing a piston Skirt....