spark plug woe

[planetdave]

Was having a misfire under load so checked the sparkies. I was a little surprised to find a broken plug - the ceramic had cracked at the join. Hairy muff but it's only been in for 300 miles and the replacement was due to the previous plug having the ceramic rotate but the core OK.

It's in the same position, what can be going on? Me being cack-handed putting it in or mechanical sinister stuff or co-incidence?

[Snake the Sniper]

Does sound a little unusual! How do you fit your spark plugs? How do you ensure they are done up tight enough?

[Texpis]

Looks like you are overheating by running lean or the timing is out have a look here. http://www.spark-plugs.co.uk/pages/technical/diagnosis.htm Just a note of caution if it is running lean it could damage your engine.

Mick

[planetdave]

The electrodes look fine - I tighten by hand until I think there has been a reasonable amount of 'give' in the washer.
I usually worry that I might overtighten a bit. Otherwise...it's a slightly tricky access and it is possible that I'm not getting the plug socket on exactly square (and thus cracking the ceramic) though the really difficult plug to access is fine.

I have had the engine running slightly advanced for a bit, but not enough to show on the electrode.

[GreenV8S]

planetdave said:

The electrodes look fine - I tighten by hand until I think there has been a reasonable amount of 'give' in the washer.
I usually worry that I might overtighten a bit. Otherwise...it's a slightly tricky access and it is possible that I'm not getting the plug socket on exactly square (and thus cracking the ceramic) though the really difficult plug to access is fine.

I have had the engine running slightly advanced for a bit, but not enough to show on the electrode.

I replied earlier but that disappeared (did you post another thread too)?

If the plug is being damaged it's possible that it is suffering from detonation. I'd give it a bit longer and see if it keeps happening, and just to the one plug or to more of them.

It's also possible the plug itself is overheating. They're designed to be in good thermal contact with the head, and if they aren't fitted properly they could be overheated. Usually that involves turning them through fixed angle once the crush washer has come up tight. Make sure you're getting them tight enough.

[rev-erend]

It might have been dropped..

Just replace it and re-check in a thousand miles.

[stevieturbo]

Oddly...I just had a broken plug myself at the weekend.

Mine can be awkward to fit, but this is one of the easier ones. I was very surprised to see it broken though...

[hackett]

stevieturbo said:

Oddly...I just had a broken plug myself at the weekend.

Mine can be awkward to fit, but this is one of the easier ones. I was very surprised to see it broken though...

I second that bizzarly my v8 started missing so obviously checked plugs and found one of the had completely sheered off halfway up the ceramic...mystery!