One Spark Plug Fouling (pics)

[FirstExplorer]

What is the cause of one spark plug fouling? The plug on the right was removed from the middle cylinder, right bank. All other plugs from remaining cylinders looked like the one on the left.

The residue is a chalky gray/white corrosion.

 

[FR-425]

White chalky build up (ash fouled) is from burning oil.

Yours is very white though: May be coolant. (check for oil in the rad or coolant in the oil) May have a cracked head or blown head gasket.

If it's not coolant: possible to clear up by switching to full synthetic oil.

It will still be burning oil in that cylinder but you will get longer life out of the plug.

It will keep on running like this for a long time.

Causes: Leaking valve seal and/or worn/broken piston ring, cylinder wall scoring.

Only a rebuild will fix the underlying problem.

 

[FirstExplorer]

Great reply. But, why only one cylinder? I have been using very high grade synthetic oil since this Explorer was new. I started with Mobil 1, which was the only synthetic on the market in the early 90s. I switched to Royal Purple and have been using that and Amsoil for the last 10 years.

Could it be a bad injector? For that cylinder?

 

[corkey]

no, not an injector, oil could be a bad ring seal, or a valve seal,, , if it's not much , i wouldn't worry about it, just keep an eye on how much oil it uses,,

it probably isn't too much,
when was the last time you changed the plugs ??

 

[FR-425]

Not fuel fouled. They would be white if lean but no build-up, black if rich.

It's either oil or coolant.

Fuel mixture won't cause this type of fouling.

 

[FirstExplorer]

I consulted my trusted mechanic on this issue, and this we may have discover the reason for this fouling.

The Explorer spark plugs are recessed deep into the manifold. A common problem is that water can get trapped in the holes above the plug.

I sprayed the engine last year with A cleaner from Gunk, then rinsed it at the car wash with a pressure sprayer. I tried to keep all electronics dry, but I am sure some water got into the recess. That particular plug, right side center plug, was right in line of the rinse.

The water shorts out the plug. My tech said this is common in Ford engines with the deep recess.

I will monitor this one plug and report back. If it fouls again, then we will know it is something else. If it is a one-off fouling problem, then it was the water. I will bump this thread in about 6 months.

 

[shucker1]

Grounded out plug due to water would give you a dead miss and turn the plug black from fuel fouling. You would feel the missing cylinder while driving.

Something else going on inside your engine.

It wouldn't be a bad idea to run a compression check while you have the plugs out.

 

[FirstExplorer]

Something else going on inside your engine.

It wouldn't be a bad idea to run a compression check while you have the plugs out.

I will do that this week. I am having my radiator fan replace due to large cracks (thanks to a warning from another member). I will have my guy do the test at that time.