Plug gaps

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MikeyBikey
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Plug gaps

Post by MikeyBikey » Wed Jul 18, 2018 7:42 am

Blimey.

Lots of short runs ? Leaving unburnt fuel on the plug ?


Is we sideways yet...

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Plug gaps

Post by philhoward » Wed Jul 18, 2018 7:48 am

I've heard of some "valve protection" additives leaving deposits on the plugs but can't remember which one it was :oops:


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Plug gaps

Post by peter freeman » Wed Jul 18, 2018 8:44 am

That looks more like water been at them.



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Plug gaps

Post by Old and Slow » Wed Jul 18, 2018 9:29 pm

A clear case of oil fouling, if you believe this chart, which some don't.
plug-colour.jpg
plug-colour.jpg (213.18 KiB) Viewed 593 times


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Old and Slow
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Plug gaps

Post by Old and Slow » Thu Jul 19, 2018 8:29 pm

Is it a high mileage engine? If so then IMO could be either valve guide seals or worn rings/bores.
I think I'd start with a dry compression test, and then add a tiny amount of oil to each cylinder in turn and repeat the compression test. If there's a 20% or more improvement when wet then I think that means it needs new rings (but someone with more experience could advise what change to expect).
Otherwise replace the valve guide stem seals?
If it is a result of mostly short trips then try a good run out and see if the oily carbon can be burned off.
Good luck.


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Plug gaps

Post by RonH » Thu Jul 19, 2018 9:24 pm

Cheers old and slow. 77,000 miles. 300 miles last year :oops: 5000 since 2011. Now the iridium plugs are fitted I’ll give the car a good run and check one of the plugs (that is apart from number 1 what a pain). I could possibly pick out a colour match for many of the oil fouled plugs and many other pictures. All except the light straw which is what I had hoped for. Valve guide seals is high on my list of suspects.
Ron (custodian of GTC 404)



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