Piston Hit Number 6 Spark Plug

[horizon33]

Hello about a year ago i had one of my big bearings go . I had them all replaced and a good condition second hand crank shaft installed . All was fine until a couple of weeks ago when my car started to have a miss when i really put my foot down but it would go back to normal about ten seconds after. But then i was just driving normally oneday and it suddenly started to miss permanantely . i changed spark plugs and it was still there i played with coil packs found out the noise of the engine would stay the same with number 6 plug . so changed front coil with back and it still stayed the same so it wasnt coilpack. At this stage i couldnt figure it out so i took it to a mechanic. He beleives that the piston has hit the spark plug and thinks its a big end bearing gone again. The cars oil pressure was fine and had no knock from the motor or flashing dash lights like last time . So im just wondering if anyone has had a similar problem. or has a better idea of what could be going on?

If it is another bearing there must be something wrong with my motor . im only running stock boost . Mechanicsaid i either get a second hand bottom end or just get new bearings. rb30 bottom end could be an idea too?

[sleptema]

Why not try unplugging number 6 injector? That would be the obvious next step for me.

I don't understand how the rod could stretch that much to hit the plug. Even if it did, the problem would not have been intermittent in the first place.

[horizon33]

Yeah i tried that too but the engine noise changed so that was fine . Yeah i dont really understand either.

[scotty nm35]

I have seen pistons hit the head, and it was making a fair noise by that stage. To hit the plug you would have to be running a longer plug than recommended. My suggestion, try another mechanic.

[sleptema]

My suggestion, try another mechanic.

I will second this.

[Plattsy]

could be hundreds of things before that mate.

coil parck harness could be stuffed on no 6.

soark plug could be cross threaded

head gasket broken, rings gone, head cracked.

a missfire can pe a pita to diagnose.

but if the piston had hit the plug youd know about it....

[Ben C34]

Sounds wrong.

But why speculate? Just pull out the plug and look at it.

[horizon33]

The mechanic has pulled the plug out and gap has closed . Thats what he told me .

[Plattsy]

you have wrong spark plug in.

simples.

bcpres11 gapped to 8mm.

go!

[zebra]

BCPR6ES

is pregapped at 0.8

no need to buy the -11

[Ben C34]

11 means 1.1 gap incase anyone is wondering.

[Plattsy]

and i thought the 6 where .6.....

thats why ive always gapped elevens. oh well you learn something new every day!

[Ben C34]

6 is heat range.

[Plattsy]

well there you go.

[Ben C34]

And funnily enough all the other letters mean something also. But no one cares....

[horizon33]

ok maybe ill try that because i know im using 1.1

[Got a Pulsar]

Yes but BCPR6ES or BKR6EYA or XYZ123AB-C???

And funnily enough all the other letters mean something also. But no one cares....

http://www.ngk.de/fileadmin/templates/Dokumente/EN/downloads_not_used_in_download_area/ngk_zuendkerzen_code_en.pdf

[GTRPSI]

Pull the plug, use a bore scope and have a look around inside.

IF you used the correct length plugs there is no way the piston would close the plug gap, the sides of the piston would hit the head first and you would hear that from a mile away.

Im wondering if you dropped a valve guide in there.....bore scope will soon find out....

Something hit your plug to close it and i highly doubt it was a piston.

There is always a possibility that the last person to fit the plug dropped it off the socket as they were fitting the plug down the hole and it closed the gap considerably, these things can happen when people are careless, ive seen this in the past on a number of engines where they didnt have the rubber sleeve to hold the plug into the socket in good condition and the plug just slides off and drops down into the head closing the gap.

Anyone who has this happen should get the plug out and recheck the gap before putting it back in.

[blind_elk]

Only time I ever had a plug close the gap, it had been hit by a chunk of piston ringland playing pinball inside the cylinder.