Diagnose this spark plug?

Joined
Jan 5, 2017
Messages
384
Location
Talkeetna AK
2003 F150 4.2l 160k miles on it

Misfire on cylinder 2, severity 2/3
had a misfire earlier on cylinder 2 for lean but thought I fixed it when I replaced the fuel filter(was really nasty) and the plugs/wires
it has returned with a vengeance.

noticing coolant levels have been going down too. I’m wondering if coolant is diagnosable on a spark plug? That plug from cylinder 2 is a little crusty white as apposed to the other ones which are just whitish.


first two photos are of cylinder 2 spark plug.
3rd and 4th photos are for comparison in cylinders 1 and 5.
these are new plugs.

thank you!
 

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Coolant into the combustion chamber will make the plug insulator snow white with no deposits present, like your first two pics..The plugs would literally be steam cleaned. If you suspect coolant, pressure test the cooling system.
 
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Here are the photos of cylinders 1 and 5
 

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Little update
Looking at that picture, realized there was oil on that plug. So caught up on finding the coolant leak as the culprit.

Went back and pulled it again.
Here is the picture
Is that the valve cover?
 

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Took some pictures with the boroscope
 

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With reference to head gasket failure and diagnosis this method has worked for me for the last 40+ years as a self-employed mechanic. No need to buy any test gear either: top up the coolant take the car for a 20 minute drive. Then allow the engine to completely cool down. At least four hours.
ANY residual pressure when you remove the pressure cap is a sure sign of a leaking head gasket. Although I work mainly on Peugeot/Citroen vehicles, it will work on most.
As long as the gasket isn't totally shot, in which case it'll be obvious, try it. I agree the plug's condition points to coolant in the cylinder.
 
Update: coolant and oil in the cylinder just didn’t add up. (Still could be coolant) unfortunately, I only git one specific cylinder misfire code. It just kept giving me p0316 codes.
Decided to check the coil pack. Hopefully I can get the video and picture of the bottom of the coil pack loaded. Note the hairline cracks on bottom of the coil pack.

Fixed it with a car-quest part and truck runs great.

 

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