Why replace your spark plugs?
Spark plugs are the heart of your vehicle's engine. For maximum fuel economy and peak engine performance, your spark plugs should be replaced every 30 months or 30,000 miles. This may vary depending on the type and model of your vehicle. This brochure will help you replace your spark plugs quickly and correctly. Although replacing plugs isn't usually difficult, be sure to READ all instructions provided.
Tools & Equipment
To replace your spark plugs you will need:
  • spark plug wrench or a spark plug socket and ratchet
  • spark plug gap gauge
  • torque wrench (optional)
  • rag or brush
  • length of 5/16" rubber hose approximately 6" long
Safety Precautions
Before replacing your spark plugs:
Proper maintenance and service procedures are vital to the safe, efficient operation of all motor vehicles, as well as to the safety of the person performing the work- you. Whenever you're working on your vehicle, we recommend that you follow these important safety rules:
  • DON'T work under a car unless it's securely supported.
  • DON'T run the engine without proper ventilation.
  • DON'T smoke when working around the engine.
  • DO have a first aid kit handy.
  • DO be careful when working around hot or sharp objects.
  • DO have adequate ventilation whenever you work with any chemicals.
Installation
Before You Begin:
  • Purchase new plugs that are the right size and heat range for your specific engine (consult a spark plug manufacturer's guide). Never rely on cross-references.
  • Allow the engine to cool completely before attempting to remove the old plugs. This is particularly true if the engine has aluminum cylinder heads.
  • Gather together all the tools and equipment you'll need before you start.
  • Adjust the new plugs to the proper gap beforehand. The correct gap for your vehicle's engine can be found in the owner's manual.

To avoid mixing up the spark plug wires, it's a good idea to remove and replace one plug at a time or use tape to label each wire.

 
  • With the engine cool, carefully remove the spark plug wire from the end of the spark plug by pulling the rubber boot. Do not pull the wire itself. If the boot sticks, use a twisting motion to pull the boot and plug wire free. (See Figure 1)

     

  • If compressed air is available, use it to blow any dirt away from the spark plug area. Otherwise, clean off the old plug and the area around it with a rag or small brush. This will help prevent any foreign material from falling into the cylinder when the plug is removed.

     

  • Remove the plug by turning it counterclockwise with a spark plug wrench or a spark plug socket and ratchet. If the plug is hard to remove, use a small amount of penetrating oil to help remove it.

Gap the new plug
  • Set the recommended gap in the new plug with a spark plug gap gauge (the correct gap can be found in your owner's manual). Insert the proper thickness wire or feeler between the inner and outer electrodes at the tip of the plug. When properly gapped, the wire or feeler should slide between the electrodes with a slight drag. If the gap is incorrect, gently bend the outer electrode slightly until the correct gap is achieved. (See Figure 2)

     

  • Make sure that the outer electrode is centered directly over the inner electrode. If it's not, align the two by gently bending the outer electrode.

Check the cylinder head threads
Visually inspect the cylinder head threads. They should be in good condition, clean, and free of dirt and debris. This new spark plug should freely screw into the cylinder head by hand. Any binding of the plug is an indication that there's a problem. Remove the plug and inspect the threads.

Install the new plug
  • Make sure that the area around the spark plug port is clean. Wipe the seat with a clean rag to ensure proper contact between the new plug and the seat.
  • Insert the plug into the spark plug hole by hand and turn it clockwise until it's snug. If the spark plug hole is hard to reach, try attaching a short piece of 5/16" rubber hose to the top of the plug and use it as an extension to help reach the hole.
  • After installing the plug be hand as far as it will go, firmly tighten it with a spark plug wrench or socket. It's a good idea to use a torque wrench, if one is available, to ensure that the plug's properly seated. DO NOT OVERTIGHTEN. Remember, you'll get an accurate torque reading only if the spark plug and cylinder head threads are clean and dry.
  • Reattach the plug wire to the new plug. Use a twisting motion on the boot until it's firmly seated on the top of the plug.
  • Repeat the above steps for each plug you're replacing.
Quick Tips
  • Follow these instructions carefully. Read and be sure you understand them before you begin.
  • Gather together all of your tools and supplies before you begin.
  • Allow plenty of time to do the job so you don't have to hurry.
  • Remember that these are general instructions. For more detailed instructions pertaining to your specific vehicle, consult an appropriate repair manual.
  • Safety is important whenever you're working around machinery. Beware of hot objects, sharp instruments and hazardous materials.
  • Don't substitute tools unless you're sure you won't compromise either your safety or the performance of your vehicle.