re: spark plug question

[quk@isham-research.demon.co.uk (Phil Payne)]

In message <86256730.0055F4F1.00@mail.mei.com> William.Elliott@mail.mei.com writes:

> Phil:  Why are you changing the W7DTC's at 8000 miles?

>  My reason for asking: My '85 UrQ  (obviously not an MB but: K24, IA stage
> 1, 14psi)
> started surging/missing under boost with W7DTC's at about 7000 miles.
> The plugs looked great, so I replaced coil/cap/rotor/wires, etc... and the
> miss was still there. All turbo/IC hoses were good.
> Replaced the plugs with another set of W7DTC's: miss goes away.
>
> Now it's 7000 miles later and my miss/surging has returned.  Again the
> plugs look great.

I think you answered your own question - or at least came up with data
very similar to ours.  The plugs are specified for some ludicrous service
interval (30,000 miles?) but quite obviously aren't up to it.  I think
the three-prong design just distributes the prong load around and perhaps
triples prong life - but it _all_ goes through the centre electrode.

As it happens, a set of plugs for the MB is only GBP10 ($16) so it's
not an issue.

--
 Phil Payne
 Phone: 0385 302803   Fax: 01536 723021
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