🔧 Grand Cherokee - Spark Plug Replacement

Replacing the spark plugs on your Grand Cherokee helps restore smooth idle, strong acceleration, and fuel efficiency. The 5.7L HEMI uses 16 spark plugs total, because each cylinder has two spark plugs.

Difficulty Level: Intermediate | Estimated Time: 2-4 hours

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⚠️ Safety & Precautions

• ⚠️ Let the engine cool completely before starting. Spark plugs thread into aluminum cylinder heads, and hot aluminum threads can be damaged easily.
• ⚠️ Disconnect the negative battery cable before unplugging ignition coils to prevent accidental electrical shorts.
• ⚠️ Do not drop anything into an open spark plug well. A spark plug well is the deep tube where the plug sits.
• ⚠️ Replace plugs one cylinder at a time so the ignition coils and wiring stay organized.
• ⚠️ Do not use anti-seize unless the spark plug maker specifically requires it. Many modern plugs have coated threads.

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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
• 3/8-inch universal joint
• Flathead screwdriver
• Needle-nose pliers
• Spark plug gap gauge
• Compressed air blow gun
• Dielectric grease
• Magnetic pickup tool
• 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
• Intake tube clamp replacement - Qty: 2 if damaged
• Ignition coil boots - Qty: 16 if cracked, swollen, or oil-soaked

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📋 Before You Begin

• Park your Grand Cherokee on level ground, shift to Park, and set the parking brake.
• Open the hood and allow the engine to cool fully.
• Use a fender cover to protect the paint while you lean over the engine bay.
• Use a 10mm socket to disconnect the negative battery cable. Move the cable aside so it cannot spring back onto the battery post.
• Work on one ignition coil and its two spark plugs at a time. This keeps everything simple and prevents mix-ups.
• A torque wrench is a tool that tightens fasteners to an exact tightness. This is very important for spark plugs.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the Engine Cover

• Use both hands to lift the plastic engine cover straight upward.
• The cover is held by rubber grommets, so no bolts usually need to be removed.
• Set the cover aside where it will not get scratched.
• Pull evenly, not sideways.

Step 2: Remove the Air Intake Tube for Access

• Use an 8mm socket or flathead screwdriver to loosen the clamp at the throttle body.
• Use an 8mm socket or flathead screwdriver to loosen the clamp at the air filter box.
• Use needle-nose pliers to release any small hose clamps attached to the intake tube.
• Lift the intake tube out of the engine bay and place it aside.
• Take a photo first.

Step 3: Blow Dirt Away From the Coil Area

• Put on safety glasses.
• Use a compressed air blow gun to clean around the ignition coils and spark plug wells.
• This prevents dirt from falling into the engine when the spark plugs are removed.

Step 4: Unplug One Ignition Coil

• Choose one ignition coil to start with.
• An ignition coil is the small electrical part on top of the spark plugs that creates the spark.
• Use your fingers to press the connector lock tab and pull the connector straight off.
• If the connector is stubborn, use a flathead screwdriver gently to help release the tab.
• Do not pull on the wires.

Step 5: Remove the Ignition Coil

• Use a 10mm socket, 3-inch extension, and 3/8-inch drive ratchet to remove the ignition coil retaining bolt.
• Twist the coil slightly by hand, then pull it straight up.
• Set the coil aside in the same direction it came out.
• Inspect the rubber boots for cracks, swelling, oil, or carbon tracking. Carbon tracking looks like thin black lightning marks.

Step 6: Remove the First Spark Plug

• Use a 5/8-inch spark plug socket, 6-inch extension, and 3/8-inch drive ratchet to loosen the first spark plug.
• A spark plug socket has a rubber insert or magnet that grips the plug so it does not fall.
• Turn counterclockwise slowly until the plug is loose.
• Lift the spark plug out carefully.
• If the plug feels stuck, stop and tighten it slightly, then loosen again slowly.

Step 7: Remove the Second Spark Plug for the Same Cylinder

• Use the 5/8-inch spark plug socket, 6-inch extension, and 3/8-inch drive ratchet to remove the second spark plug under the same ignition coil area.
• Use the 3/8-inch universal joint if the angle is tight near the firewall.
• A universal joint is a swivel adapter that lets the socket work at an angle.
• Lift the spark plug out carefully.

Step 8: Check the New Spark Plug Gap

• Use a spark plug gap gauge to verify each new plug gap before installation.
• The spark plug gap is the small air space where the spark jumps.
• For the 5.7L HEMI, set the gap to 0.043 in. / 1.1 mm unless the replacement plug manufacturer states the plug is pre-gapped and should not be adjusted.
• Do not pry against fine-wire iridium or platinum center electrodes.

Step 9: Install the New Spark Plugs by Hand First

• Place one new spark plug into the 5/8-inch spark plug socket.
• Use the 6-inch extension by hand only to start threading the spark plug clockwise.
• Turn it several full turns by hand before using the ratchet.
• This prevents cross-threading, which means the plug is going in crooked and damaging the cylinder head threads.
• Repeat for the second spark plug in the same cylinder.
• Hand-start every plug.

Step 10: Torque the Spark Plugs

• Use a 5/8-inch spark plug socket, extension, and 3/8-inch drive torque wrench to tighten each spark plug.
• Torque to 18 Nm (13 ft-lbs)
• Do not overtighten. The cylinder heads are aluminum and can be damaged.

Step 11: Reinstall the Ignition Coil

• Apply a small amount of dielectric grease inside each ignition coil boot.
• Dielectric grease is a non-conductive grease that helps seal moisture out of the boot.
• Push the ignition coil straight down until fully seated.
• Use a 10mm socket and 3/8-inch drive torque wrench to tighten the ignition coil retaining bolt.
• Torque to 8 Nm (71 in-lbs)
• Reconnect the electrical connector until it clicks.

Step 12: Repeat for the Remaining Cylinders

• Repeat Steps 4 through 11 for each ignition coil.
• Your Grand Cherokee has 8 cylinders and 16 spark plugs total.
• Use the 3/8-inch universal joint and 3-inch or 6-inch extension as needed for tight rear plugs.
• Keep the old plugs lined up in order so you can compare them later.
• One cylinder at a time.

Step 13: Reinstall the Air Intake Tube

• Position the intake tube back between the air filter box and throttle body.
• Use an 8mm socket or flathead screwdriver to tighten both hose clamps snugly.
• Reconnect any small hoses using needle-nose pliers if needed.
• Make sure the tube is fully seated and not folded at the ends.

Step 14: Reinstall the Engine Cover and Battery Cable

• Push the engine cover straight down onto its rubber mounts by hand.
• Use a 10mm socket to reconnect the negative battery cable.
• Tighten the battery terminal snugly. Do not overtighten the clamp.

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✅ After Repair

• Start the engine and let it idle for 1-2 minutes.
• Listen for smooth idle and check that there are no warning lights.
• If the engine misfires or shakes, shut it off and recheck that every ignition coil connector is fully clicked in.
• Take a short test drive and confirm smooth acceleration.
• After the test drive, open the hood and recheck the intake tube clamps with an 8mm socket or flathead screwdriver.
• If the battery was disconnected, the radio presets, clock, and auto-up window memory may need to relearn or be reset.

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💰 DIY vs Shop Cost

Shop Cost: $450-$850 (parts + labor)

DIY Cost: $120-$280 (parts only)

You Save: $330-$570 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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