Spark plug diagnostic question

Hudson N

Member
Aug 7, 2018
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8
Queen creek Arizona
This doesn't look right, is it oil fouling, what do you guys think?
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90sickfox

Wasn't a pretty sight...and I've got big hands
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That's a sign of oil being in the combustion chamber....

What cylinder was that and what engine ?
 

CarMichael Angelo

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Nov 29, 1999
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5.0 ho out of my 1991 mustang. That was cylinder 5. I figured it was oil fouling, I think its valve seals.
That spark plug looks like its been in the engine for 12000 miles.

It would be wet if it was fouling. It looks to be neither fuel, nor oil. Most likely carbon
Build up.
If the engine eats oil enough to foul a plug, it'd smoke as well I think.
And unless you've either did a leak down test ( preferred) or a compression test to determine overall consistency between cylinders, I'd think twice before pulling anything apart.
 

Hudson N

Member
Aug 7, 2018
50
3
8
Queen creek Arizona
That spark plug looks like its been in the engine for 12000 miles.

It would be wet if it was fouling. It looks to be neither fuel, nor oil. Most likely carbon
Build up.
If the engine eats oil enough to foul a plug, it'd smoke as well I think.
And unless you've either did a leak down test ( preferred) or a compression test to determine overall consistency between cylinders, I'd think twice before pulling anything apart.

She smoked a little. But replaced my PCV and it hasn't smoked much since. Should I put some new plugs in, factory plugs instead of those Bosh plugs the previous owner put in?
 

90sickfox

Wasn't a pretty sight...and I've got big hands
SN Certified Technician
Mar 2, 2015
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Bosch plugs don't like fords....

Change plugs....send it...then check them...