1997 GMC Suburban Fouling #6 spark plug

1997 GMC SUBURBAN
168,000 MILES • V8 • 4WD • AUTOMATIC
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RBUNCE
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I have a 1997 GMC Suburban with 168000 miles. I have developed an issue with my number 6 spark plug. I is fouling out after a few days and my check engine light will come on and after a few days the light will go off. I pulled the plug out and found a light colored carbon deposit on it. There was heavy oil on the threads. I changed out the intake/exhaust valve stem seals. All seamed good. A day later, number 6 fouls again. My next step is to change my intake manifold gasket but I do not want to chase my tail. There is no, repeat no signs of coolant in the oil! What do you think?
Jan 3, 2010 at 1:29 PM
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DOCFIXIT
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What's cyl compression? plug wire resistence in limits?
Jan 7, 2010 at 3:15 PM
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RBUNCE
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Resistance on #6 spark plug wire is 1.02 using the 20k scale. I personally do not know what the limits are to determine a go/no-go result.
Next is the compression. 120 psi done multiple time to verify.

Thanks
Jan 9, 2010 at 10:12 AM
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DOCFIXIT
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Plug wire O.K. compression a tad weak , is code P0306? do you ever get P0300? What color is deposit on plug?
Plug type Ac 41-932?
Jan 9, 2010 at 1:19 PM