Ash Buildup On Plug #5

[BlueTahoe98]

I have a 98 Tahoe 350 cu in. A month ago I was getting a loss of power and hesitation. Eventually I got a check engine alert. The scanner told me it was a misfire for cylinder #5. Cylinder 5 was covered in heavy ash. I replaced the plugs and wires and power has been restored. After 250 miles I noticed that the ash is developing again on the electrode side of the insulator on plug #5. I checked the #1 and #3 plug, as well. The othe plugs were so clean you could eat off them. Any ideas? Is this indicative of a mechanical problem i.e. head or electrical?

 

[lesterl]

Could be oil, what color is the ash? Does it use oil? Have you run a compression test?

 

[StreetStylen]

Intake manifold gasket leak, I just had the same issue with p0306, Coolant leaks into the chamber and causes a misfire. Not saying its what is wrong but it is very common with this motor. If your ashy buildup is brown/orangish or a shade of the coolant you are running I would start looking into taking the top half off the motor. Mine was really bad, 2 coolant passages where gummed up and the gasket was in 3 pieces. 230,000 miles on mine now.

 

[largewon62]

My 97 does the same thing on #3 plug........mine has a white ashy fluffy deposit and I get a P0303 code (misfire cyl.3) sometimes at idle.

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