[Component Inspection]

Check the spark plug for any damage on its thread and insulator.
If there is damage, replace the spark plug.
Check the electrode. Measure the insulation resistance with an ohmmeter.
If the resistance is less than the specified value, adjust the electrode gap

Specification : 10 MΩ or more

Fig 1: Measuring Insulation Resistance With Ohmmeter
Courtesy of KIA MOTORS AMERICA, INC.
Check the spark plug electrode gap.
If the gap is greater than the maximum, replace the spark plug

Specification: 1.0 - 1.1 mm (0.0394 - 0.0433 in.)

NOTE:

If adjusting the gap of a new spark plug, bend only the base of the ground electrode. Do not touch the tip.
Never attempt to adjust the gap on a used plug.

Fig 2: Adjusting Gap Of Spark Plug

Courtesy of KIA MOTORS AMERICA, INC.