Oil in spark plug well, but not on electrode. Where from? - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars
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post #1 of 74 (permalink) Old 01-17-19, 08:06 PM Thread Starter
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Oil in spark plug well, but not on electrode. Where from?

I have a 1997 Grand Marquis. It had a misfire a few months ago in cylinder #5. I changed all plugs, and saw there was oil on the plug, above the seal. That is, it must have benn in the spark plug well. There was no oil on the threads, or the electrode.

The misfire went away,

Then two days ago, I started getting a backfire, from near the engine compartment, and a slightly stumbling idle.

Pulled plug #5, and there was oil on it again. (see picture). I cleaned it, and the backfire stopped.

Two days later I noticed a slight stumble, and pulled the plug, and the oil was there again.

I am assuming the misfire (two months ago), and the current backfire, and stumble, are related to this #5 plug. I did see a misfire code tow months ago, but as threre was not misfire (yet, anyway) for this plug this time.
Where is oil coming from? valve cover?


This is the clean plug:
spark plug 1.jpg

This is the oiled plug:

spark plug 3.jpg

spark plug 2.jpg

This is a picture of the plug pars (roughly the same as mine, the oil is above the area labeled 'SEAL SURFACE'):
spark_plug parts.jpg

The spark plug hole is NOT in the valve cover:
https://www.fordforums.com/attachmen...1&d=1547784316

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File Type: jpg spark plug hole.jpg (94.5 KB, 7 views)
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post #2 of 74 (permalink) Old 01-17-19, 08:12 PM Thread Starter
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Re: Oil in spark plug well, but not on electrode. Where from?

(BTW, I've had P430, O2 sensor below threshold for over a year now, but think that is not the cause of either the misfire, backfire, or stumbling).
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post #3 of 74 (permalink) Old 01-17-19, 09:49 PM
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Its more likely coolant coming from the intake manifold. The gaskets on my 02 gt were leaking and got nasty coolant in the spark plug wells of cylinders 5,6 and 7.
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post #4 of 74 (permalink) Old 01-18-19, 02:45 AM
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Re: Oil in spark plug well, but not on electrode. Where from?

The oil on plug body can cause the spark to track which will give intermittent misfire . Check for any oil leaks , possibly from valve covers. Always better to to replace boots and apply dielectric grease .
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post #5 of 74 (permalink) Old 01-18-19, 10:53 AM Thread Starter
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Re: Oil in spark plug well, but not on electrode. Where from?

Where is the dielectic grease applied? Around the plug? Around the boot? All over the boot, or just near the top of the boot to keep oil out?
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post #6 of 74 (permalink) Old 01-18-19, 10:55 AM Thread Starter
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Re: Oil in spark plug well, but not on electrode. Where from?

I was thinking it was oil based on the color.

I suppose it could be coolant, that was made dark from dirt and grime on the engine?

How could I test to distinguish if it's oil, versus coolant?

I am also adding 1 quart every 600 to 800 miles, so the oil is being lost somewhere, although I was guessing mostly it was from a bad seal around the oil pan...

I also add a small amount of coolant (about 1/4" in the coolant reservoir, every 6 months).
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post #7 of 74 (permalink) Old 01-18-19, 02:05 PM
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Re: Oil in spark plug well, but not on electrode. Where from?

Quote:
Originally Posted by mnalep View Post
Where is the dielectic grease applied? Around the plug? Around the boot? All over the boot, or just near the top of the boot to keep oil out?
Just put a dab inside the end of the boot that slides over the plug. Doesn't take much.
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post #8 of 74 (permalink) Old 01-18-19, 09:26 PM Thread Starter
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Re: Oil in spark plug well, but not on electrode. Where from?

How does the dialectic grease help?
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post #9 of 74 (permalink) Old 01-18-19, 10:11 PM
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You can smell it, coolant will have a distinct smell. And most likely the valve stem seals are bad allowing oil into the chambers and its burning the oil. Bad valve stem seals are a common problem for 97- 4.6 2v motors.

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02 Gt Mineral Grey
Steeda Sport Springs, 3.73s, Pro5.0 Short Shifter, Pypes O/r X Pipe, full 2.5 inch exhaust with M80's, 75mm Tb and C&L Plenum

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post #10 of 74 (permalink) Old 01-19-19, 01:43 AM
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Re: Oil in spark plug well, but not on electrode. Where from?

If valve stems you usually get plenty of symptoms showing , carbon buildup on valves . oil on plug electrode , blue smoke to name a few .

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