Spark Plug: Removal

Remove the ignition coil (12029). For additional information, refer to IGNITION COIL .

NOTE: Remove any foreign material from the spark plug wells with compressed air before removing the spark plugs (12405).

Fig 1: Removing Spark Plugs

Courtesy of FORD MOTOR CO.

Remove the spark plugs.
Inspect the spark plugs for a bridged gap.
- Check for deposit build-up closing the gap between the electrodes. Deposits are caused by oil or carbon fouling.
- Clean the spark plug.
Fig 2: Inspecting Spark Plugs For Bridged Gap
Courtesy of FORD MOTOR CO.
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.
Fig 3: Checking Spark Plug For Oil Fouling
Courtesy of FORD MOTOR CO.
Inspect for carbon fouling. Look for black, dry, fluffy carbon deposits on insulator tips, exposed shell surfaces and electrodes, caused by a spark plug with an incorrect heat range, dirty air cleaner, too a rich fuel mixture or excessive idling.
- Clean the spark plug.
Fig 4: Checking Spark Plug For Carbon Fouling
Courtesy of FORD MOTOR CO.
Inspect for normal burning.
- Check for light tan or gray deposits on the firing tip.
Fig 5: Checking Spark Plug For Normal Burning
Courtesy of FORD MOTOR CO.
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.
- Install a new spark plug.
Fig 6: Checking Spark Plug For Melted Electrodes And Damaged Insulator
Courtesy of FORD MOTOR CO.
Inspect for overheating, identified by a white or light gray-brown spots and with 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.
Fig 7: Checking Spark Plug For Overheating
Courtesy of FORD MOTOR CO.
Inspect for fused deposits, identified by melted or spotty deposits resembling bubbles or blisters. These are caused by sudden acceleration.
- Clean the spark plug.
Fig 8: Checking Spark Plug For Fused Deposits
Courtesy of FORD MOTOR CO.
Adjust the spark plug gap as required.

Fig 9: Identifying Spark Plug Gap Adjusting Dimensions
Courtesy of FORD MOTOR CO.