One spark plug fouling over time

tackepj · April 30, 2006

I have a 1995 K1500 W/T with the 4.3 V6 and 5-spd. About a year ago it started hesitating during low-speed acceleration. I changed the plugs and wires, and one of the plugs was covered in gray/tan crusty ash, enough to ground the electrode. All the other plugs were fine. Now, a year later, the same problem is happening with the same plug. I replaced the plug again and it's better, but I pulled it out again last night and it was starting to collect crud again.

The Haynes manual says it's likely due to valve guide seals, but I don't use any more oil than I ever did (<1 qt between changes) and it doesn't smoke at startup. It's only this plug, all the others are perfect.

Any ideas? I was thinking fuel injectors, but it's TBI, so wouldn't that affect other cylinders too?

Thanks in advance.

MemphisDoug · May 5, 2006

How is the sparkplug wire going to that plug? Maybe the wire is bad causing the plug to miss-fire at times.

tackepj · May 8, 2006

How is the sparkplug wire going to that plug? Maybe the wire is bad causing the plug to miss-fire at times.

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Well, I replaced the wires after the first time the plug fouled, and it didn't seem to help. Does seem ignition related though. I also replaced the cap and rotor last year too...

yekots · August 6, 2006

I ran into this plus the cutting out with my 98. I ended up replacing the coil and went the an MSD coil. All is good now after 1100 miles. I have 97K on my truck right now.

Hope it helps.

KICK · August 20, 2006

oil fouled plugs are usually black so that doesn't sound like the problem.

TBI has 2 injectors, it is kind of a Y system that feeds 2 outside cyl's on one head and 1 middle cyl on other head with fuel. generaaly if injector problem on TBI you lose 3 cycls on the V6. so that aint the problem either.

that leaves you with ignition problem on one particular cylinder or vacuum/compression leak at the offending cylinder.

did it actually foul the plug this time or it was just ash coated?

maybe you can try a hotter plug on that cylinder

mcreyaufmiller · August 22, 2006

I have a similar problem with my 98 on #6, but mine is oil fouling from a leaky guide seal. I ordered a new motor and until it is in, I just replace the plug every couple months.