How to Replace the Spark Plugs in Cars

by Contributing Writer; Updated June 12, 2017

The spark plugs in a HEMI 5.7 engine need to be replaced every 30,000 miles. The spark plugs are what create the spark necessary to ignite the fuel in the combustion chamber. When the plugs go bad, you won't be able to start your HEMI. Replacement plugs can be purchased at any auto parts store. Once you have the new plugs, you'll need to know how to replace them.

Under The Hood:

 How to Replace Spark Plugs in an Alero

Find the spark plugs in your Oldsmobile Alero. In most engines, such as the 2.2L model, the spark plugs are right on top of the engine block and are easily accessed. For a 2.4L engine, the spark plugs are underneath the black engine cover on top of the engine, which can be removed by unscrewing the support screws. 3.1L engines require the air filter be removed to access the plugs, while a 3.4L engine requires the removal of the windshield wiper cover. Refer to your owner's manual for the technical details pertaining to your specific vehicle.

Remove the spark plug wire from one spark plug by squeezing the cap at the end of the wire and pulling straight away from the engine, not at an angle. Do not pull on the wire itself, only on the wire end. This should expose a chamber with a spark plug within.

Lower your socket into the spark plug chamber until it fits snugly around the spark plug. Rotate the socket wrench counterclockwise until the spark plug comes away freely from the engine. Remove only one spark plug and wire at a time, and do not move on to the next plug until the wire has been reattached. Mixing up the spark plug wires can cause serious damage to the engine.

Apply some anti-seize compound to your new spark plug, using just a small amount around the screw threads on the end. This will help your spark plug maintain a good connection. Lower the spark plug into your vehicle with the socket wrench until it fits in place. Rotate clockwise until the plug becomes fairly tight, then give it an additional 1/16th of turn to give it the correct amount of torque.

Items you will need

  • New spark plugs

  • Socket wrench

  • 5/8-inch socket or spark plug socket

  • Anti-seize compound

  • Screwdriver

  • Owner's manual

 How to Replace Spark Plugs in a Cadillac Escalade

Pop the hood and look at the engine. The spark plug wires are located on the right and left sides of the engine. If the Cadillac Escalade has a six-cylinder engine, there are three spark plugs on the right side and three spark plugs on the left side. If the SUV has an 8-cylinder engine, there are four spark plugs on either side of the engine. These plugs are located halfway down the engine, slightly lower than the height of the battery. Spark plug wires are generally red with black tips.

Remove the spark plug wire from the end of the spark plug. Grab the tip of the spark plug wire. It is the cushioned part of the spark plug wire attached to the spark plug. Never pull the spark plug wire by the wire itself.

Place the 16 mm socket over the spark plug and attach the wrench. Turn the socket counter-clockwise one to two turns to loosen the spark plug.

Remove the socket from the spark plug and turn the plug with your hand until it comes out of the engine.

Clean the inside of the spark plug wire with the wire brush. Lightly brush away any debris or corrosion inside the tip.

Insert the new spark plug into the engine. Consult the owner's manual for the correct spark plug part number for the year the Escalade was manufactured.

Tighten the spark plug into the slot with your hand. Once it is tight, use the socket and wrench to tighten the spark plug about 1/4 of a turn more.

Replace the spark plug wire and repeat Steps 1 through 7 for the remaining spark plugs. If a spark plug wire is connected to the wrong cylinder, the Escalade will have problems firing, which causes problems with the engine.

Items you will need

  • 16 mm socket

  • Socket wrench

  • New spark plugs

  • Wire brush

 How to Replace Spark Plugs in a GMC Sierra

Disconnect the negative battery cable and allow the engine to cool.

Find the spark plugs on the vehicle that are located on the sides of the engine. Some of the GMC Sierra engines have a rubber flap covering the sides. Remove the flap to gain access to the spark plugs.

Take the spark plug wire by the boot and turn it to release the lock. Pull back on the spark plug wire by the boot. This removes the wire from the spark plug revealing the spark plug.

Cover the spark plug with the socket. Use the extension and the socket wrench to unscrew the spark plug. Pull the spark plug out of the cylinder head.

Spray silicone onto the threads of the spark plug and insert the new spark plug into the socket. Use the socket and wrench to thread the new spark plug in place. Gently turn the spark plug to the right to start the threading process. Never force the spark plug into the bore.

Connect the spark plug cable to the end of the spark plug and remove the next spark plug cable. Repeat the above process for the rest of the spark plugs.

Connect the battery cable and replace the rubber flap, if removed in Step 2.

Items you will need

  • Spark plug socket

  • Socket wrench with extension

  • Silicone spray

  • New spark plugs

  • Tension testing tool

 How to Replace the Spark Plugs in a HEMI 5.7

Open the hood and pull one of the spark plug wires off of the top of the engine. Only work on one spark plug at a time.

Attach the socket extension to the spark plug socket and lower the socket into the engine.

Remove the spark plug by turning the socket counterclockwise with a socket wrench.

Pull the spark plug and socket out of the engine.

Pull the spark plug out of the spark plug socket.

Insert a new spark plug socket and thread it into the spark plug socket hole. Tighten the spark plug and replace the plug wire.

Repeat steps 1-5 for all spark plugs on the engine.

Items you will need

  • Spark plug socket

  • Socket wrench

  • Socket extension

 How to Change the Spark Plugs on a 1999 Mercury Marquis

Check the gap on the base of all eight new Motorcraft AWSF-32P, or equivalent, spark plugs with a spark plug gap tool. The correct gap for the Grand Marquis’s 4.6-liter engine is 0.052 to 0.056 inches. Replace any incorrectly gapped spark plugs for new ones, as these plugs are not adjustable.

Remove the retaining screw on the center rear of the engine cover with a Phillips screwdriver and pull the cover off the engine.

Remove the two smaller hoses plugging into the air cleaner outlet hose by pulling each hose away from the air cleaner outlet hose. Loosen the hose clamps securing both ends of the air cleaner outlet hose with a Phillips screwdriver.

Pull both ends of the hose from their connection points and remove the hose from the engine compartment.

Look on the top of the engine, just inward from the valve covers, and find the eight coil packs – four on each side.

Press and hold the locking button on one coil pack's wiring harness and pull the wiring harness from the coil pack. Remove the coil pack retaining bolt with a ratchet and socket. Pull the coil pack upward with a slight twisting motion to remove it.

Blow the spark plug tube out with compressed air to remove any debris surrounding the spark plug. Remove the spark plug with a ratchet, 6-inch extension and spark plug socket.

Pull the spark plug from the spark plug socket – a rubber insert inside the socket holds it in place. Insert a new spark plug into the spark plug socket until the rubber insert holds it in place.

Hand-thread the spark plug into the engine with the spark plug socket and 6-inch extension. Attach a torque wrench to the extension, and tighten the spark plug to 15 foot-pounds.

Squeeze a small amount of dielectric grease inside the coil pack’s rubber boot and spread it around the inside of the boot with a small flat-head screwdriver. Line up the coil pack boot with the top of the new spark plug and press the coil pack onto the spark plug until you feel it click into place.

Line up the coil pack's bolt hole with the bolt hole in the cylinder head. Hand-tighten the coil pack retaining bolt, then tighten it from 7 to 8 foot-pounds with a torque wrench and socket. Plug the wiring harness back into the receptacle on the top of the coil pack.

Repeat Steps 6 through 11 to replace the remaining seven spark plugs.

Press the air cleaner outlet hose ends back onto the air cleaner box and throttle body inlets. Tighten the two hose clamps with a Phillips screwdriver. Plug the two smaller hoses into their respective holes in the air cleaner outlet hose.

Set the engine cover back on top of the engine and tighten its retaining screw with a Phillips screwdriver.

Items you will need

  • Spark plug gap tool

  • 8 Motorcraft AWSF-32P

  • Phillips screwdriver

  • Ratchet

  • Socket set

  • Compressed air

  • 6-inch extension

  • Spark plug socket

  • Torque wrench

  • Dielectric grease

  • Small flat-head screwdriver

 How to Replace the Spark Plugs on a Northstar

Open the hood of the vehicle and disconnect the cables from the battery before you proceed. Look on the right and left side of the engine block and locate the spark plugs. On the V8 engine there will be eight spark plugs and on V6 engines there will be six.

Remove the wires that are connected to the tip of each plug one at a time so that you don't mix them up. Remove the spark plugs one at a time using the Northstar tool. Place the thin edge of the spark plug gapper between the pin in the center of the plug and the metal arm over the pin.

Turn the gapper until the metal arm lines up with the gap setting for that specific engine. Insert the new spark plug into the engine and tighten the plug until it is snug using the Northstar tool. Replace the wire to the tip of the spark plug and repeat for all other spark plugs.

Items you will need

  • Northstar plug remover

  • Replacement spark plugs

  • Spark plug gapper

 How to Replace the Spark Plugs on a 2002 Buick Lesabre

Open the hood and look at the top of the engine where the spark plug wires run into the cylinder head. Grip the boot on the spark plug wire to the far left with your hand and twist it in place on the cylinder head. Then pull it out of the head and place it to the side.

Remove the spark plug from the engine with the ratchet, extension and spark-plug socket. Throw out the old plug.

Use the spark plug gapping tool to gap the replacement plug to 0.060 inch (six hundreths of an inch). Then install the plug into the stock location with the ratchet, extension and spark plug socket. Push the spark plug wire back onto the plug. When it clicks in place, it's locked onto the plug properly.

Repeat steps 1 through 3, moving from left to right across the cylinder head until they are all replaced.

Items you will need

  • 3/8-inch ratchet and extension

  • Spark plug socket

  • Spark plug gapping tool

  • Replacement spark plugs

 How to Change the Spark Plugs on a 2002 Oldsmobile Alero

Open the hood of the Alero, and set the hood prop. Remove the cover from the top of the engine, using a ratchet and socket to remove the four mounting bolts. Pull the cover straight upward then remove it from your work area. The coil is mounted under the cover, and will come off with it.

Remove the old spark plug farthest to the passenger side of the engine, using a 3/8-inch drive ratchet, a 6-inch extension, and a spark plug socket. Turn the plug counterclockwise to remove it.

Check the gap on the new spark plug with a feeler gauge or spark plug gap tool. Adjust the gap to 0.045 inches, if necessary.

Remove extension and spark plug socket from the ratchet. Install the new spark plug into the spark plug socket. Thread the new spark plug in by hand, until it is snug. Tighten the spark plug to 180 inch-pounds of torque with a 3/8-inch-drive torque wrench.

Repeat Steps 2 through 4 from left to right on the engine, until you have replaced all of the spark plugs.

Install the ignition coil and cover back onto the top of the engine. Install it straight downward, so the coil plugs mate with their respective spark plug holes. Push down until you feel it "snap" into place. Tighten the mounting bolts to 180 inch-pounds of torque.

Items you will need

  • 3/8-inch drive ratchet

  • 3/8-inch drive, 6-inch extension

  • 3/8-inch drive spark plug socket

  • 4 new spark plugs

  • 3/8-inch drive torque wrench

 How to Change Spark Plug on Polaris Scrambler 500

Removing the Spark Plug

Rotate and remove the spark plug cap covering the Scrambler 500's spark plug, located underneath the front rack in the quad's single cylinder.

Rotate the spark plug counterclockwise with a spark plug wrench.

Gently lift the spark plug out of the hole.

Inspecting and Installing the New Plug

Check the condition of the original spark plug. A normal plug is gray, tan or light brown in color. If the original is burnt, flaky and white, or cracked, replace it with a new BKR6E spark plug.

Measure the spark plug gap, which is the gap between the hook and the electrode end of the plug. It should measure exactly 0.036 inch.

Gently push the hook end of the spark plug against a firm surface if the spark plug gap is greater than 0.036 inch. Stop when the gap meets the correct measurement.

Insert a spark plug gap tool into the gap and gently enlarge the gap if it is too small. Stop when the gap measures 0.036 inch.

Install the spark plug using the spark plug wrench, turning the plug clockwise into its hole in the Scrambler 500's cylinder. Return the spark plug cap and return the front rack before starting the engine.

Items you will need

  • Spark plug wrench

  • Spark plug gapping tool

  • BKR6E spark plug (0.036 inches)

 How to Replace the Spark Plugs on a 1999 Buick Century

Open the hood to access the engine compartment. Locate the sparkplug wires in the front of the engine. The wires can be traced from the coil pack mounted behind the engine. Follow the bright orange wire to the front of the engine that is plugged in to the engine cylinder.

Pull the sparkplug wire by gently twisting and pulling it out. This will expose the sparkplug.

Unscrew the sparkplug by placing a 5/8" deep well socket attached to the socket wrench over the sparkplug and unscrewing it from the engine cylinder.

Replace with the new sparkplug. Insert the new sparkplug and screw it in by hand. Tighten the sparkplug with a socket wrench to ensure it is tight.

Push the sparkplug wire on to the end of the sparkplug and push. The wire will lock in place.

Repeat steps to replace each spark plug. You may need to stand on a step ladder to reach the back three spark plugs.

Items you will need

  • Socket wrench

  • 5/8' deep well socket

  • Step ladder

 How to Change Spark Plugs in a GS300 Lexus

Measure the gap for each of the new spark plugs with the feeler gauge. The "gap" is the space between the filament and the firing point at the top of the spark plug. You measure the space in between the firing point and the filament with the appropriate blade on feeler gauge. In this case, the gap for the Lexus spark plugs should be .044 thousandths. Spark plugs are factory set but you should still check each one.

Pull the spark plug wire off the plug by grasping the boot as close to the engine as possible and pulling it gently away from the spark plug. Remove the plug from the cylinder head using the spark plug socket and ratchet and discard it.

Place a new plug in the cylinder head of the GS300. Tighten it with the ratchet and spark plug socket. Be careful not to cross-thread the plug or you will damage the cylinder head. Plug the spark plug wire back on the plug. Repeat the process on the next plug.

Items you will need

  • Spark plug socket

  • Ratchet

  • Feeler gauge

 How to Change the Spark Plugs on a Lincoln Navigator

Open the hood on your Lincoln Navigator by pulling on the release handle located just above the brake at the bottom of the instrument panel then prop it up with the support rod.

Remove the coil pack and clean the well and valve area thoroughly with compressed air. Pour tuneup cleaner into the well, filling it to just above the jamb nut. Let it soak for at least 15 minutes for best results.

Twist the spark plug back and forth until it's removed. This may take a bit of effort. The spark plugs are located under a panel that is connected to the engine compartment usually with one bolt. Under the panel you will find the spark plugs each with their own coil pack.

Coat the electrode shield with lubricant but do not coat the strap. Replace all of the spark plugs and the coil pack. When complete, close the hood.

Items you will need

  • Compressed air

  • Tuneup cleaner

  • Lubricant

 How to Replace the Spark Plugs on a 2005 GMC Yukon Denali

Disconnect the negative battery cable, loosening the nut with a wrench. Check the gap on the new spark plugs with a feeler gauge. The gap on the plugs should be .040. Insert the feeler gauge blade into the gap at the top of the plug. It should fit snugly. Plugs are factory set, but you need to check them anyway.

Pull one spark plug wire off the plug. Grasp the boot close to the engine and pull it off. Do not pull on the wire or you could break the filament inside. Remove the spark plug with a spark plug socket, ratchet and extension. Discard the old plug.

Put the new plug into the cylinder head and tighten it snugly. Be careful not to cross-thread the spark plug in the cylinder head or you will damage it. Place the spark plug wire onto the new plug and push it in until you feel it snap into place. Repeat the process on the next spark plug until you change them all.

Items you will need

  • Spark plug socket

  • Ratchet

  • Extension

  • Wrench set

  • Feeler gauge

About the Author

This article was written by the It Still Runs team, copy edited and fact checked through a multi-point auditing system, in efforts to ensure our readers only receive the best information. To submit your questions or ideas, or to simply learn more about It Still Runs, contact us.