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HOMESERVICE MANUALSLINCOLN2015MKS BASE, AWDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 28 (ENGINE SYSTEM - GENERAL INFORMATION)GENERAL PROCEDURESSPARK PLUG INSPECTION
2015 Lincoln MKS Base, AWD

Spark Plug Inspection

2015 Lincoln MKS Base, AWDSECTION Spark Plug Inspection
WARNING: This page is about a different car, the 2015 Lincoln MKT. However, it is still accessible from the selected car via links, so may be relevant.

  • 1.

    Inspect the spark plug for a bridged gap.
    • Check for deposit build-up closing the gap between the electrodes. Deposits are caused by oil or carbon fouling.
    • Install a new spark plug.
GFD91361Courtesy of FORD MOTOR COMPANY

  • 2.

    Check for oil fouling.
    • Check for wet, black deposits on the insulator shell bore electrodes, caused by excessive oil entering the combustion chamber through worn rings and pistons, excessive valve-to-guide clearance or worn or loose bearings.
    • Correct the oil leak concern.
    • Install a new spark plug.
GFD91362Courtesy of FORD MOTOR COMPANY

  • 3.

    Inspect for carbon fouling. Look for black, dry, fluffy carbon deposits on the insulator tips, exposed shell surfaces and electrodes, caused by a spark plug with an incorrect heat range, dirty air cleaner, too rich a fuel mixture or excessive idling.
    • Install new spark plugs.
GFD91363Courtesy of FORD MOTOR COMPANY

  • 4.

    Inspect for normal burning.
    • Check for light tan or gray deposits on the firing tip.
GFD91364Courtesy of FORD MOTOR COMPANY

  • 5.

    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 unauthorized installation of a heli-coil insert in place of the spark plug threads.
    • Install a new spark plug.
GFD91365Courtesy of FORD MOTOR COMPANY

  • 6.

    Inspect for overheating, identified by white or light gray spots and a bluish-burnt appearance of electrodes. This is caused by engine overheating, wrong type of fuel, loose spark plugs, spark plugs with an incorrect heat range, low fuel pump pressure or incorrect ignition timing.
    • Install a new spark plug.
GFD91366Courtesy of FORD MOTOR COMPANY

  • 7.

    Inspect for fused deposits, identified by melted or spotty deposits resembling bubbles or blisters. These are caused by sudden acceleration.
    • Install new spark plugs.
GFD91367Courtesy of FORD MOTOR COMPANY
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.