🔧 Grand Cherokee - Spark Plug Replacement

Replacing the spark plugs on your Grand Cherokee helps restore smooth idle, strong acceleration, and proper fuel economy. The 5.7L HEMI 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

• ⚠️ Let the engine cool completely before starting. Spark plugs thread into aluminum cylinder heads, and hot aluminum is easier to damage.
• ⚠️ Disconnect the negative battery cable to reduce the chance of accidental electrical shorting while working near ignition coils.
• ⚠️ Work on one ignition coil and plug area at a time so wires and coils do not get mixed up.
• ⚠️ Do not allow dirt or debris to fall into the spark plug wells. Clean around each coil before removal.
• ⚠️ Do not overtighten spark plugs. The cylinder heads are aluminum and can be damaged by excess torque.

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🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 13mm 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 adapter
• Flathead screwdriver
• Needle-nose pliers
• Compressed air blow gun
• Spark plug gap gauge
• Dielectric grease
• Anti-seize compound
• 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
• Ignition coil boots - Qty: 16 if worn, cracked, oil-soaked, or swollen
• Throttle body gasket - Qty: 1 if throttle body is removed for access

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📋 Before You Begin

• 🅿️ Park your Grand Cherokee on level ground, shift to Park, and set the parking brake.
• ❄️ Let the engine cool for at least 2-3 hours before removing spark plugs.
• 🔋 Use a 10mm socket to disconnect the negative battery cable and move it aside so it cannot spring back onto the terminal.
• 🧼 Blow dirt away from the top of the engine with compressed air before opening any spark plug wells.
• 📏 Check each new spark plug gap before installation. Use the plug specification listed on the under-hood emissions label when available.
• ℹ️ A spark plug socket has a rubber insert or magnet inside to hold the plug so it does not fall while installing or removing it.
• ℹ️ A universal joint adapter is a small swivel that helps your socket reach angled or tight spark plugs.

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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.
• Lift the plastic engine cover straight upward by hand to release it from the rubber mounting grommets.
• Set the cover aside where it will not get scratched or stepped on.
• Pull upward evenly.

Step 2: Disconnect the Battery

• Use a 10mm socket and 3/8-inch drive ratchet to loosen the negative battery terminal nut.
• Lift the negative cable off the battery post and tuck it aside.
• Make sure the cable cannot touch the battery post while you work.

Step 3: Clear Access Around the Ignition Coils

• Use a flathead screwdriver to gently release any plastic wire loom clips that block access to the ignition coils.
• Use needle-nose pliers only if a clip is stubborn. Pull on the clip, not the wires.
• If the air intake tube blocks your reach, use an 8mm nut driver or flathead screwdriver to loosen the intake tube clamp, then move the tube aside.
• Do not disconnect more than needed. Keep the layout easy to remember.

Step 4: Clean the First Coil Area

• Choose one ignition coil to start with.
• Use a compressed air blow gun to clean dirt from around the ignition coil and spark plug well.
• This prevents grit from falling into the cylinder when the spark plug is removed.
• Clean first, remove second.

Step 5: Disconnect the Ignition Coil Connector

• Press the connector lock tab with your thumb or a small flathead screwdriver.
• Pull the connector straight back from the ignition coil.
• Do not pull on the wires.

Step 6: 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 ignition coil gently by hand to loosen the rubber boots.
• Pull the coil straight upward and out of the spark plug wells.
• Inspect both rubber boots for cracking, oil swelling, or carbon tracking. Carbon tracking looks like thin black lightning marks.

Step 7: Remove the First Spark Plug Under That Coil

• Use a 5/8-inch spark plug socket, 6-inch extension, and 3/8-inch drive ratchet to loosen the first spark plug.
• If access is angled, use the 3/8-inch universal joint adapter between the socket and extension.
• Turn counterclockwise slowly until the plug is fully unthreaded.
• Lift the spark plug out carefully using the spark plug socket.
• If the plug feels stuck, stop and work it back and forth gently. Do not force it.

Step 8: Remove the Second Spark Plug Under That Coil

• The 5.7L HEMI has two spark plugs per cylinder.
• Use the 5/8-inch spark plug socket, 6-inch extension, and 3/8-inch drive ratchet to remove the second spark plug in the same coil area.
• Use the 3/8-inch universal joint adapter if needed for clearance.
• Compare the old plugs. Heavy oil, fuel smell, broken porcelain, or uneven wear can point to another engine issue.

Step 9: Check and Prepare the New Spark Plugs

• Use a spark plug gap gauge to verify the gap on each new plug.
• Use the spark plug gap shown on your under-hood emissions label if it is present.
• Apply only a very small amount of anti-seize compound to the spark plug threads if the plug manufacturer does not already coat the threads.
• Do not get anti-seize on the electrode tip.
• Too much anti-seize affects torque.

Step 10: Install the First New Spark Plug by Hand

• Place the new spark plug into the 5/8-inch spark plug socket.
• Use the 6-inch extension by hand only to start threading the plug clockwise.
• Thread it several turns by hand before using a ratchet. This prevents cross-threading.
• Once seated, use a 3/8-inch drive torque wrench and 5/8-inch spark plug socket to tighten it to Torque to 18 Nm (13 ft-lbs).

Step 11: Install the Second New Spark Plug

• Use the same 5/8-inch spark plug socket and 6-inch extension to start the second spark plug by hand.
• After it threads smoothly and seats, use the 3/8-inch drive torque wrench to tighten it to Torque to 18 Nm (13 ft-lbs).
• Do not exceed the torque spec.

Step 12: Reinstall the Ignition Coil

• Apply a small dab of dielectric grease inside each ignition coil boot. Dielectric grease helps seal out moisture but does not conduct electricity.
• Push the ignition coil straight down over both spark plugs until it seats fully.
• Install the coil retaining bolt with a 10mm socket and 3/8-inch drive torque wrench.
• Tighten the ignition coil bolt to Torque to 8 Nm (71 in-lbs).
• Reconnect the electrical connector until it clicks.

Step 13: Repeat for the Remaining Cylinders

• Repeat Steps 4-12 for the remaining seven ignition coils.
• Replace both spark plugs under each coil before moving to the next coil.
• Use the 3-inch extension, 6-inch extension, and 3/8-inch universal joint adapter as needed for the rear cylinders.
• The rear plugs near the firewall are the tightest. Take your time and keep the socket straight.
• One coil at a time.

Step 14: Reinstall Any Moved Intake or Wiring Parts

• Use a flathead screwdriver to reinstall any wire loom clips you released.
• If the air intake tube was moved, reinstall it fully onto the throttle body and air box.
• Use an 8mm nut driver or flathead screwdriver to tighten the intake tube clamp snugly.
• Make sure no wires, hoses, or tools are left on the engine.

Step 15: Reconnect the Battery and Reinstall the Engine Cover

• Reconnect the negative battery cable to the battery post.
• Use a 10mm socket and 3/8-inch drive ratchet to tighten the terminal nut snugly.
• Press the engine cover straight down by hand until the rubber grommets seat.

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✅ After Repair

• ✅ Start your Grand Cherokee and let it idle for 1-2 minutes.
• ✅ Listen for a smooth idle. A misfire, shaking, or check engine light usually means a coil connector is loose or a coil boot is not fully seated.
• ✅ Check that the air intake tube is fully attached and clamped.
• ✅ Take a gentle 10-minute test drive. Acceleration should feel smooth with no hesitation.
• ✅ If the clock or one-touch window settings changed after battery disconnect, reset them using the normal interior controls.

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💰 DIY vs Shop Cost

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

DIY Cost: $120-$250 (parts only)

You Save: $300-$500 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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🎯 Ready to get started?

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