🔧 Grand Cherokee - Spark Plug Replacement

Replacing the spark plugs on your Grand Cherokee restores proper ignition, smooth idle, and fuel economy. The 5.7L HEMI V8 uses two spark plugs per cylinder, so this job requires replacing 16 spark plugs total.

Difficulty Level: Intermediate | Estimated Time: 2.5-4 hours

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⚠️ Safety & Precautions

• ⚠️ Work only on a completely cold engine. The cylinder heads are aluminum and can be damaged if hot.
• ⚠️ Disconnect the negative battery cable before unplugging ignition coils.
• ⚠️ Wear safety glasses when blowing debris away from the spark plug wells.
• ⚠️ Do not use an impact tool on spark plugs.
• ⚠️ Start every spark plug by hand before tightening with a ratchet or torque wrench.

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🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 8mm socket
• 5/8-inch spark plug socket
• 3/8-inch drive ratchet
• 3/8-inch drive torque wrench
• 3-inch extension
• 6-inch extension
• 10-inch extension
• 3/8-inch drive universal joint adapter
• Spark plug gap gauge
• Compressed air blow gun
• Flathead screwdriver
• Needle-nose pliers
• Fender cover
• Nitrile gloves
• Safety glasses

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Spark plugs - Qty: 16
• Dielectric grease - Qty: 1 tube
• Throttle body gasket - Qty: 1, only if throttle body is removed for extra access

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📋 Before You Begin

• Park your Grand Cherokee on level ground and set the parking brake.
• Let the engine cool completely before starting.
• Use a 10mm socket to disconnect the negative battery cable.
• Check each new spark plug with a spark plug gap gauge. Use 0.043 in / 1.1 mm gap unless the plug maker says not to adjust it.
• A spark plug socket is a deep socket with a rubber insert or magnet that holds the plug.
• A universal joint adapter is a small swivel that helps your socket reach angled rear plugs.
• Work on one ignition coil at a time so the plug boots and connectors do not get mixed up.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the Engine Cover

• Put on safety glasses and nitrile gloves.
• Place a fender cover over the fender you are leaning across.
• Lift the engine cover straight upward by hand to pop it loose from its rubber mounts.
• Set the cover aside where it will not get stepped on.
• Lift evenly with both hands.

Step 2: Disconnect the Battery

• Use a 10mm socket with the 3/8-inch drive ratchet to loosen the negative battery cable clamp.
• Move the negative cable away from the battery post so it cannot touch again by accident.

Step 3: Remove the Air Intake Tube

• Use an 8mm socket or flathead screwdriver to loosen the clamp at the throttle body.
• Use needle-nose pliers to release any small hose clamps attached to the intake tube.
• Pull the air intake tube off by hand and set it aside.
• This makes more room to reach the ignition coils.

Step 4: Unplug One Ignition Coil

• Choose one ignition coil to start with.
• Press the electrical connector lock tab by hand and slide the connector off the coil.
• If the tab is stubborn, gently press it with a flathead screwdriver.
• Do not pull on the wires.

Step 5: Remove the Ignition Coil

• Use a 10mm socket, 3/8-inch drive ratchet, and 3-inch extension or 6-inch extension to remove the coil retaining bolt.
• Twist the coil slightly by hand to loosen the rubber boots.
• Pull the coil straight upward and remove it.
• Each coil covers two spark plugs on this engine.

Step 6: Clean Around the Spark Plug Wells

• Use a compressed air blow gun to blow dirt and grit away from both spark plug wells.
• Keep your safety glasses on because debris can fly upward.
• This step keeps dirt from falling into the engine when the plugs come out.

Step 7: Remove the First Spark Plug

• Attach the 5/8-inch spark plug socket to a 6-inch extension or 10-inch extension.
• Use the 3/8-inch drive ratchet to turn the spark plug counterclockwise.
• After it breaks loose, spin it out by hand using the extension.
• Lift the old spark plug out carefully.
• For tight rear plugs, add the 3/8-inch drive universal joint adapter.

Step 8: Install the First New Spark Plug

• Check the new plug gap with a spark plug gap gauge. Target gap is 0.043 in / 1.1 mm.
• Place the new spark plug into the 5/8-inch spark plug socket.
• Thread the plug into the cylinder head by hand using only the extension.
• If the plug does not turn easily, remove it and start again.
• Use the 3/8-inch drive torque wrench to tighten the plug to Torque to 18 Nm (13 ft-lbs).
• Hand-starting prevents thread damage.

Step 9: Replace the Second Spark Plug Under the Same Coil

• Use the 5/8-inch spark plug socket, extension, and 3/8-inch drive ratchet to remove the second plug.
• Check the new plug gap with the spark plug gap gauge.
• Install the new plug by hand first using the extension.
• Use the 3/8-inch drive torque wrench to tighten it to Torque to 18 Nm (13 ft-lbs).

Step 10: Reinstall the Ignition Coil

• Apply a small dab of dielectric grease inside each coil boot. Dielectric grease is a non-conductive grease that helps keep moisture out.
• Push the coil straight down by hand until both boots seat onto the spark plugs.
• Install the coil retaining bolt using the 10mm socket.
• Use the 3/8-inch drive torque wrench to tighten the coil bolt to Torque to 8 Nm (71 in-lbs).
• Reconnect the coil electrical connector until it clicks.

Step 11: Repeat for the Remaining Cylinders

• Repeat Steps 4 through 10 for the other seven ignition coils.
• Use the 3/8-inch drive universal joint adapter and longer extensions for the rear cylinders where space is tight.
• Replace both plugs under each coil before moving to the next coil.
• Confirm you replaced 16 spark plugs total.

Step 12: Reinstall the Air Intake Tube

• Push the air intake tube back onto the throttle body by hand.
• Reconnect any hoses using needle-nose pliers if clamps were removed.
• Use an 8mm socket or flathead screwdriver to tighten the intake clamp snugly.

Step 13: Reconnect the Battery

• Place the negative battery cable back onto the battery post.
• Use a 10mm socket and 3/8-inch drive ratchet to tighten the clamp snugly.
• Do not overtighten the battery clamp.

Step 14: Reinstall the Engine Cover

• Line up the engine cover with its rubber mounts.
• Push the cover down by hand until it seats firmly.

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✅ After Repair

• Start your Grand Cherokee and let it idle for 2-3 minutes.
• Listen for rough idle, ticking, hissing, or misfires.
• If it runs rough, shut it off and recheck each ignition coil connector.
• Take a short test drive and confirm smooth acceleration.
• If the check engine light flashes, stop driving and recheck your work before continuing.

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💰 DIY vs Shop Cost

Shop Cost: $450-$750 (parts + labor)

DIY Cost: $120-$260 (parts only)

You Save: $330-$490 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 2-3 hours.

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