Spark Plug Replacement
How are spark plug issues diagnosed?
If the spark plugs are suspected, they're checked for proper connection with the ignition coil. If that's OK, the plugs must be removed, and the spark plug gap must be checked.
If the gap is too small because of corrosion, or too large because or deterioration, they will be replaced. If the spark plug is in good condition, a tester is used to find whether the spark plug is able to produce spark.
How is a spark plug replaced?
On newer vehicles, spark plug replacement involves removing the engine cover, ignition coil harness and ignition coils, and then finally the spark plugs. For most older vehicles, removing the spark plug wires and spark plugs is all that's required.
Once the spark plugs are removed, the gap on the new spark plug is set, and the plug is installed using an anti-seize compound and proper torque. Prior to reinstalling the spark plug wire or ignition coil, dielectric grease is applied to the spark plug terminal to promote the transfer of electricity.
RepairPal recommendations for spark plug issues
Following your carmaker's recommended maintenance means the spark plugs will be changed before they become faulty, which will save you money on diagnostic fees.
What to look out for when dealing with spark plug issues
The cost of spark plug replacement can be surprisingly low or very high — it all depends on how many spark plugs need to be replaced, how hard it is to get to them, and how much diagnosis is required to identify them as the problem.