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Spark Plug lasted 30 days


Active Member
December 21, 2011
Reaction score
City, State
Port Byron, IL
Year, Model & Trim Level
2006 Mercury Mountaineer
I changed out the plugs (Autolite HT1 Platinums) and coils a month ago.

Last week I noticed a hesitation (misfire) around 55 mph, but no CEL. Well, the CEL started blinking yesterday, so I was able to get a code. Misfire cylinder 1.

Pulled the coil and it was really sooty. Pulled the plug and it was worse and without an electrode.

Has anyone had a new plug distruct in that short of time? Is there something that's perhaps causing this, internally?

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Does it look like the electrode melted or broke off? either is possible. Are you sure they were the correct heat range?

broke off. jagged edge where they were connected

Some possibilities... A defect in manufacturing, which would be the best case scenario, or the piston hit it, which is unlikely, or perhaps a faulty injector is causing a lean condition in that cylinder overheating it and causing pre-detonation.... Have you looked at all the other plugs? they look normal?

I pulled cyl 2 and it looked fine.

The guy at O'Reillys thought it could be a defect as well. He was more amazed at how the plug is designed

I’d replace them all with standard replacement Motorcraft parts. Pull it again in a few hundred miles. Might be worth a compression check if you have access to a tester.