Expedition 4WD V8-4.6L SOHC VIN W (1999)
5. Inspect for carbon fouling
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Look for black, dry, fluffy carbon deposits on insulator tips, exposed shell surfaces and electrodes, caused by a spark plug with a incorrect heat
range, dirty air cleaner, too rich fuel mixture or excessive idling.
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Clean the spark plug.
6. Inspect for normal burning.
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Check for light tan or gray deposits on the firing tip.
7. Inspect for pre-ignition, identified by melted electrodes and a possibly damaged insulator. Metallic deposits on the insulator indicate engine
damage. This may be caused by incorrect ignition timing, wrong type of fuel or the installation of a heli-coil insert in place of the spark plug
threads.
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Install a new spark plug.
8. Inspect for overheating identified by a white or light gray-brown spots and white bluish-burnt appearance of electrodes. This is caused by engine
overheating, wrong type of fuel, loose spark plugs, spark plugs with a incorrect heat range, low fuel pump pressure or incorrect ignition timing.
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Install a new spark plug.
