[s-cars] Loose spark plug detector!

J. Khang jhlk99 at yahoo.com
Tue Jun 10 12:08:27 EDT 2003

Hello everyone. Here's a tip for those of you whose
S-cars suffer from loose spark plug syndrome.

I started suffering from this after I cleaned the
combustion chamber with Redex because the threads
became clean as a whistle.

Anyway, I got a bit tired of dismantling the spark
plug cover to check the torque every week so I started
thinking about a means of determining plug torque

It turns out that you can do this from the dashboard
using the mpg display. My daily commute is very short
and involves a very repeatable drive so I reset the
meter every morning and monitor the mpg achieved when
I get to work.

The difference in mpg for my S6 between loose plugs
and freshly tightened plugs is 18-19 mpg vs. 22.5-24
mpg. This is a cold engine and I am going down a hill
but the fact is that there is a 20-25% difference on
average so this is a useable system.

Further to that, if you are plagued by loose spark
plugs then you want to tighten the plugs when the
engine is warm or partly warm. I tightened mine after
running the engine for 2-3 minutes and found a very
large improvement.

I suspect that the expansion of the aluminium head
when it is hot is allowing plugs installed when the
head was cold to rattle loose. This effect should be
accentuated if you install the plugs in winter.

'96 S6

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