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So what are my plugs telling me is wrong?

680 Views 4 Replies 5 Participants Last post by  PMI
I meant to post this last week, but I just haven't had the chance.
When I changed my plugs, I was a little surprised to find the old ones looking like this:

Sorry for the crummy pictures, my camera refused to focus on them close up.
Anyway, if you can't tell, they look really blackened around the outside, and then white on the prong that the electrode arcs over to. The blackness would suggest to me that I'm running rich, while the white prongs have me thinking either that I have coolant in my combustion chambers or that I am running really hot (i.e. lean).
Clearly I don't really know what's going on, so maybe some of you could help me troubleshoot?

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The Haynes manual doesn't seem to distinguish the discoloring of the thread area, I have the same outer coloring as you. Perhaps some fuel just get stuck on that part and sits and burns to an black ooze there. But for the electrode stuff:

"Normal- Grey-brown deposits, lightly coated core nose. Plugs ideally suited to engine, and engine in good condition."

"Overheating- Electrodes have glazed appearance, core nose very white- few deposits. Fault- plug overheating. Check- plug value, ignition timing, fuel octane rating (too low) and fuel mixture (too weak)."

"Heavy Deposits- A build up of crusty deposits, light-grey sandy color in appearance. Fault- often caused by worn valve guides, excessive use of upper cylinder lubricant, or idling for long periods."
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