🔧 Grand Cherokee - Spark Plug Replacement

Replacing the spark plugs restores strong ignition, smooth idle, and fuel economy. On your Grand Cherokee’s 4.7L V8, plug access is tight at the back, so taking your time and keeping parts organized matters.

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

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⚠️ Safety & Precautions

• ⚠️ Work on a cold engine to avoid burns and damaged threads.
• ⚠️ Disconnect the negative battery cable before unplugging ignition coils.
• ⚠️ Do not over-tighten spark plugs—aluminum heads strip easily.
• ⚠️ Keep dirt out of plug holes; blow out debris before removing plugs.

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🔧 Required Tools

You'll need the following tools for this repair:

• 8mm socket
• 10mm socket
• 1/4" drive ratchet
• 3/8" drive ratchet
• 3/8" drive torque wrench (10-30 ft-lbs range)
• 1/4" drive extension set (3", 6")
• 3/8" drive extension set (6", 10")
• Universal joint adapter 3/8"
• 5/8" spark plug socket
• Needle-nose pliers
• Trim clip removal tool
• Compressed air blow gun
• Feeler gauge (spark plug gap tool)
• Small pick tool
• Shop light
• Fender cover
• Nitrile gloves
• Safety glasses

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Spark plugs (OEM-specified type) - Qty: 8 or 16
• Dielectric grease - Qty: 1
• Ignition coil boots - Qty: 8

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📋 Before You Begin

• Park on level ground, shift to Park, and set the parking brake.
• Open the hood and let the engine cool fully.
• Use a 10mm socket to disconnect the negative battery cable and isolate it so it can’t spring back.
• Take photos before unplugging anything.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover and intake tube (if equipped)

• Remove the engine cover fasteners with an 8mm socket or release the grommets by lifting straight up (varies by cover style).
• Loosen the intake tube clamps with an 8mm socket and move the tube aside for more room.

Step 2: Identify whether your 4.7L uses 8 or 16 spark plugs

• Look at one cylinder bank with a shop light.
• If you see one plug per cylinder under each coil: you need 8 plugs.
• If you see two plugs per cylinder (often one under a coil and a second nearby): you need 16 plugs.
• Replace plugs in matching sets.

Step 3: Work one cylinder at a time (prevents mix-ups)

• Choose one coil, unplug it, and finish that cylinder before moving to the next.

Step 4: Unplug and remove the ignition coil

• Press the electrical connector lock and unplug it (use a small pick tool gently if the lock is stuck).
• Remove the coil hold-down bolt with a 10mm socket.
• Twist the coil slightly, then pull it straight out.
• Reinstall later with Torque to 8 Nm (71 in-lbs) using a torque wrench.

Step 5: Clean the plug well before removing the plug

• Blow out dirt around the plug with a compressed air blow gun.
• This keeps debris from falling into the cylinder.

Step 6: Remove the spark plug

• Use a 5/8" spark plug socket, 3/8" drive ratchet, and an extension set to loosen and remove the plug.
• For tight rear plugs, add a universal joint adapter 3/8" as needed.

Step 7: Check and prep the new spark plug

• Check the gap with a feeler gauge and set it to the spec on the plug box/underhood label.
• If the plugs are iridium/platinum, do not force-bend the tiny center electrode.
• Do not use anti-seize unless the plug manufacturer specifically requires it (most modern plated plugs do not).

Step 8: Install the new spark plug (prevent cross-threading)

• Place the new plug into the 5/8" spark plug socket.
• Thread it in by hand using a 3/8" drive extension only (no ratchet yet) until it’s fully seated.
• Tighten with a torque wrench: Torque to 20 Nm (15 ft-lbs).

Step 9: Reinstall the coil and connector

• Apply a small amount of dielectric grease inside the coil boot (this helps prevent moisture and future sticking).
• Push the coil straight onto the plug until it seats firmly.
• Install the coil bolt with a 10mm socket, then Torque to 8 Nm (71 in-lbs) with a torque wrench.
• Reconnect the electrical connector until it clicks.

Step 10: If equipped with 16 plugs, repeat for the second plug on each cylinder

• Locate the paired plug for that cylinder and repeat Steps 5 through 9.
• If a secondary plug uses a short wire/boot instead of a coil, remove it by twisting and pulling, then reinstall it fully seated.
• Do not mix up any plug wires—swap one at a time.

Step 11: Reinstall intake tube and engine cover

• Reinstall the intake tube and tighten clamps with an 8mm socket.
• Reinstall the engine cover using an 8mm socket or press it into the grommets.

Step 12: Reconnect the battery

• Reconnect the negative battery cable using a 10mm socket.

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✅ After Repair

• Start the engine and let it idle 1-2 minutes. It should run smooth with no flashing check-engine light.
• If it runs rough, shut it off and re-check: coil connectors fully clicked, coils seated, and no swapped plug wires (if equipped).
• Take a short test drive, then recheck for any intake tube looseness or hissing (vacuum leak sound).

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💰 DIY vs Shop Cost

Shop Cost: $300-$700 (parts + labor)

DIY Cost: $60-$250 (parts only)

You Save: $240-$450 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 2-4 hours.

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🎯 Ready to get started?

HowToo makes it easy: same-day/2-day shipping on every part, plus all the tools and specialty tools you need! Check out the parts and tools sections below to add everything to your cart.