Replacing Spark Plugs

To keep your car's engine running efficiently, the spark plugs and, if necessary, spark plug wires, should be changed at their maintenance interval. Old and worn out spark plugs lead to weak combustion which robs your car of power and fuel efficiency. Depending on what vehicle you drive, doing a spark plug job can be anywhere from easy to difficult.

Always follow the factory recommended maintenance interval found in your owner's manual when servicing your vehicle.

Instructions and photos courtesy of Andrew and Peter.

The Patient
The car featured in this spark plug how-to article is a 1999 Nissan Altima, the same one as can be seen here. This car has four spark plugs located on the top of the engine, making this one of the easiest spark plug jobs you will ever find!

Before you begin you will need to gather the tools and parts necessary to change the spark plugs. In this case we will need:
  • Four spark plugs for this vehicle (OEM/NGK recommended)
  • Dialectic Grease
  • Anti-Seize Compound
  • Spark Plug socket (a spark plug socket has special padding to protect the porcelain section of the spark plug)
  • Ratchet with long (at least 6") extension
  • Spark Plug gap tool (wire loop type recommended for platinum plugs)

1. Clean the Area around the spark plugs so that when the plugs are removed no dirt or debris will get into the engine.
2. Pull the Spark Plug Wire Boot straight up and off the first spark plug. You may have to twist it back and forth while pulling up to free the boot from the end of the spark plug. Always make sure that you pull on the boot and NOT the wire! (Fig. A)
3. Insert the Spark Plug Socket and remove the spark plug. (Fig. B)
4. Clean the Spark Plug Wire Boot with a clean rag. (Fig. C)5. Gap the New Spark Plug to the specified gap (0.042").
Note on gapping spark plugs: If you have "Double Platinum" type spark plugs you need to be very careful when gapping them. You can very easily break the platinum tip off the ground electrode!

6. Apply Anti-Seize Compound to the spark plug threads. This will keep the spark plugs from getting stuck in the engine. (Fig. D)
7. Install the New Spark Plug. Start by fully seating the spark plug into the spark plug socket, this way the socket will hold the spark plug and prevent it from falling and bending the ground electrode. Once it starts to thread properly, tighten it to its proper torque rating (between 14 and 22 ft. lbs.). If you do not have access to a torque wrench, tighten the spark plug to where you have to start putting a little bit of force into the wrench, then another quarter to half turn. It should not be over tightened and 14-22 ft. lbs does not require much effort when using a ratchet. (Fig. E)
8. Apply Dialectic Grease to the spark plug wire boot. (Fig. F)9. Install the Wire Boot by pressing it firmly down onto the spark plug.
10. Continue Until All the Spark Plugs Have Been Changed. Work on one plug at a time to avoid mixing up the spark plug wires.

  1. Remove spark plug wire boot from spark plug.
  2. Remove old spark plug.
  3. Gap new spark plug.
  4. Apply anti-seize to spark plug threads.
  5. Install new spark plug.
  6. Apply dialectic grease to spark plug wire boot.
  7. Install spark plug wire boot.

The reason replacing spark plugs on this car is so easy is due to their easy accessibility. On other vehicles, especially 'V' type engines (i.e. V6, V8) the spark plugs can be difficult to reach. If you have a V6 front wheel drive car you will be able to reach 3 of the 6 plugs without a problem, but the other 3 will be hard.
Changing spark plugs is one of those iconic jobs that comes to mind when a "tune-up" is mentioned. In this case it was a quick, easy, and inexpensive job and was worth doing.

Relevant Sites
Here is an external link to a site with information relevant to this article.


Garage Equipment January 9, 2013 at 5:20 AM  

Put a very small amount of anti-seize lubricant on the plug threads if you are installing them in an aluminum engine. The anti-seize prevents a reaction between dissimilar metals.

Grogan's Mill Shell February 1, 2017 at 1:09 PM  

Some drivers make repairs on their own so, we advise car owners before jumping into a do-it-yourself repair. For example, drivers should always read their owner's manual before assuming their check engine light problems are due to the spark plugs. Also, be careful with the ignition coils since these parts connect to the spark plugs as well. Great outline for replacing spark plugs though!

fortywinks32 July 2, 2018 at 4:19 AM  

This is a nice and informative, containing all information and also has a great impact on the new technology. Thanks for sharing it


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