How to Change Your Spark Plugs

Before You Start

It’s important to allow your vehicle’s engine to cool completely, especially if it has aluminum cylinder heads.

You should also follow these essential safety rules anytime you do work on your vehicle:

• Have a first-aid kit handy.
• Be careful when working around hot or sharp objects.
• Follow the manufacturer’s instructions for all products.
• Use safety stands under the vehicle’s frame or drive-on ramps if you have to raise your vehicle.
• Ensure you have proper ventilation before you turn on the engine.
• Don’t smoke when working around the engine.

Installation

Read these instructions completely before you begin.

You’ll need to purchase new spark plugs that are the right size and heat range for your vehicle’s engine. You can find these specifications by checking the manufacturer’s recommendation or by using our spark plug selector on www.NAPACanada.com.

Adjust the Gap of the New Spark Plugs

Most spark plugs these days have preset gaps, so you don’t have to adjust them. If your spark plugs need to be adjusted, here’s what to do:

• Look up the correct gap for the new spark plugs in your vehicle’s owner’s manual.
• Choose the correct measurement on yourand insert the gauge between the inner and outer electrodes at the tip of the plug. When the plug is 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 you’ve achieved the correct gap.
• Make sure that the outer electrode is centred directly over the inner electrode. If the electrodes aren’t aligned, gently bend the outer electrode until it’s in position.

Remove the Old Spark Plugs

Remove and replace the old plugs one at a time or use tape to label each wire so that you don’t mix them up.

• Once the engine has cooled, pull the rubber boot to carefully remove the spark plug wire from the end of the spark plug. Do not pull the wire itself. If the boot sticks, use a twisting motion to pull it and the plug wire free.
• If you have access to compressed air, use it to blow away any dirt 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 keep foreign material from falling into the cylinder when you remove the plug.
• Remove the plug by turning it counter-clockwise 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.

Check the Cylinder Head Threads

• Visually inspect the cylinder head threads. They should be in good condition, clean, and free of dirt and debris. Each new spark plug should be easy to screw into the cylinder head by hand. If any of them binds up, you have a problem. Remove the plug and inspect the threads.

Install the New Spark Plugs

• Make sure that the area around the spark plug port is clean, and wipe the seat with a clean rag. You want 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, attach a short piece of 5/16-inch rubber hose to the top of the plug to create a kind of extension.
• After screwing in the plug by hand as far as it will go, firmly tighten it with a spark plug wrench or socket. If you have a torque wrench, it’s a good idea to use it. Using a torque wrench will ensure the plug is properly seated. Do not over-tighten. And remember: the only way you’ll get an accurate torque reading is if the spark plug and cylinder head threads are clean and dry.
• Reattach the plug wire to the new plug and 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.