So what do we think caused this?

[(steven)]

The girlfriend reported her car was running rough.

Head of the spark plug seems to have fallen off in the cylinder......

How do we think this has happened?

[TheEnd]

I think that might be more bad luck than anything else, the plug doesn't look to be burnt or discoloured, maybe the plug was knocked or bent and has a crack in the ground electrode.

[Rupert Rigsby]

Faulty plug maybe, I'd be more concerned with where the electrode has finished up.

[T1pper]

Hopefully the electrode has gone out the exshaust valve and out of harms way.
But I bet it is now mashed into the top of the piston.

[kamilb1998]

I seem to recall a chap on another forum encountering the same problem. He thought it was simply an unlucky one from a batch of bad plugs.

[Steve_D]

[quote=(steven).....How do we think this has happened?.....
[/quote]

Just bad luck.

Steve

[The Black Flash]

Rupert Rigsby said:

Faulty plug maybe, I'd be more concerned with where the electrode has finished up.

Might be worth sticking a magnetic stick down the plug hole just on the off chance the broken bit is loose in there.

[PaulKemp]

How much is the car ?
I think I would use the magnetic probe to see if I can grab anything then do a compression test to see if any of the valves have suffered

Compression test result low
Put spoon of oil down plug hole
Retest if normal the rings have damage
If still low the valves have damage

If compression ok and no bits removed with magnet probe tell girlfriend she best get breakdown cover and start saving for a new car

[stevieturbo]

More than likely the bit will be long gone, If it came off in one large piece probably less chance of doing any bad damage.

Smaller pieces can get trapped down the side of the piston and score the bore and damage rings.

What make of plug was it, and had anyone ever tried to adjust the gap ?

For a normal n/a engine, such a failure would be vary rare

[Old Merc]

Stick a new set of plugs in it and if it runs and sounds OK forget about it.More than likely its in the Cat or the silencer,or imbedded in the top of the piston.Its highly unlikely to have caused any damage.

[one eyed mick]

As said above replace all of them if it running ok with no nasty noises say thank you to the great car man in the sky and drive it

[(steven)]

Thanks for the info guys

one eyed mick said:

As said above replace all of them if it running ok with no nasty noises say thank you to the great car man in the sky and drive it

Stuck a hoover and magnet down the hole, didn't get much apart from some black metallic dust in the spark plug hole (nothing in the cylinder).

Plugs have been replaced. ECU wasn't very happy though and kept throwing error codes and stalling the engine after a couple of minutes.

Reset the ECU last night but it was still dropping into limp home mode under heavy load. However a long drive only using partial throttle "seems" to have "cured" it.

As for strange noises, as I don't drive the car that much we have been playing the "was that noise there before game".

Time will tell.

stevieturbo said:

What make of plug was it, and had anyone ever tried to adjust the gap ?

OEM GM plugs (so not sure who actually makes it). Car has a full Vauxhall service history.

PaulKemp said:

Do a compression test

That was my first thought when I saw the plug but you can't even do one of those without plugging the thing into a computer........

[TheEnd]

steven said:

stevieturbo said:

What make of plug was it, and had anyone ever tried to adjust the gap ?

OEM GM plugs (so not sure who actually makes it). Car has a full Vauxhall service history.

I was thinking something along the same lines. Most plugs are pre gapped, but if for example someone dropped it and then had to bend it back, they might have started a crack at the base where it split.

Edited by TheEnd on Sunday 2nd June 15:05

[PaulKemp]

As long as you can crank the car on the starter you can do a compression test just remove all the plugs and leads so it doesn't fire then crank with throttle open