🔧 Grand Cherokee - Spark Plug Replacement

Your Grand Cherokee’s 5.7L Hemi uses 16 spark plugs (two per cylinder). You’ll remove the ignition coils, change the plugs, and reinstall everything carefully with the correct torque.

Difficulty Level: Intermediate (patient beginner OK) | Estimated Time: 3–4 hours

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⚠️ Safety & Precautions

• ⚠️ Work only on a completely cold engine to avoid burns and damaging aluminum threads.
• ⚠️ Disconnect the negative battery cable to avoid accidental sparks or short circuits.
• ⚠️ Keep tools and hardware away from the fan and belt area so nothing falls into moving parts.
• ⚠️ Do not over-tighten spark plugs; the cylinder heads are aluminum and can strip easily.
• ⚠️ Use a torque wrench (tool that clicks at a set tightness) so you don’t guess the tightness.

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🔧 Required Tools

You'll need the following tools for this repair:

• 🧰 3/8" drive ratchet
• 🧰 1/4" drive ratchet
• 🧰 10mm socket
• 🧰 8mm socket
• 🧰 5/8" spark plug socket
• 🧰 3/8" drive extension (6")
• 🧰 3/8" drive extension (3")
• 🧰 3/8" drive universal joint (swivel)
• 🧰 Inch-pound torque wrench (30–200 in-lbs)
• 🧰 Foot-pound torque wrench (5–80 ft-lbs)
• 🧰 Small flathead screwdriver
• 🧰 Needle-nose pliers
• 🧰 Feeler gauge set
• 🧰 Compressed air can or air blow gun
• 🧰 Magnetic pickup tool
• 🧰 Shop rags
• 🧰 Fender cover or clean blanket
• 🧰 Mechanic’s gloves
• 🧰 Safety glasses

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• 🛠️ Spark plugs (correct spec for 5.7L Hemi) - Qty: 16
• 🛠️ Dielectric grease (for coil boots) - Qty: 1 small tube
• 🛠️ Anti-seize compound - Qty: 0 (not recommended for these plugs)
• 🛠️ Shop towel pack - Qty: 1
• 🛠️ Battery terminal protector spray - Qty: 1 (optional)

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📋 Before You Begin

• 🧭 Park the Grand Cherokee on level ground, shift to Park, and set the parking brake.
• 🧊 Let the engine cool for at least 1–2 hours until it is fully cold.
• 🔌 Open the hood and remove the engine cover by pulling it straight up; it’s held by rubber grommets.
• 🔋 Disconnect the negative battery cable using a 10mm socket and move the cable aside so it cannot spring back.
• 🏷️ Take a quick photo of each side of the engine so you can see where wiring and coils sit before removal.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Understand the layout (16 plugs total)

• The 5.7L Hemi has 8 cylinders, but each cylinder has 2 spark plugs, so you will replace 16 plugs.
• On each side of the engine (left and right) you will see 4 ignition coil packs. Each coil serves 2 plugs via short plug wires.
• Do one cylinder at a time to avoid mix-ups.

Step 2: Remove the engine cover

• Use your hands to pull up at the front corners of the plastic engine cover.
• Lift the rear of the cover and remove it; set it somewhere clean.
• If there are any small hoses or sound insulators clipped to it, gently unclip them by hand or with a small flathead screwdriver.

Step 3: Start with the easy-access bank

• Choose the side with more room (usually passenger side on the Hemi in the Grand Cherokee).
• Identify one coil pack: it is a black module with a wiring connector and two short plug wires coming out of it.
• Take a close-up photo of this coil and wires.

Step 4: Unplug the ignition coil electrical connector

• Press the locking tab on the coil’s electrical connector with your thumb or a small flathead screwdriver.
• Gently pull the connector straight off the coil. Do not pull by the wires.
• Repeat for only the coil you are working on; leave the others connected for now.

Step 5: Remove the coil pack mounting bolts

• Use a 10mm socket and 3/8" drive ratchet to remove the bolts holding that coil to the valve cover.
• There are usually two 10mm bolts per coil pack; keep them in a small container.
• When reinstalling later, tighten these bolts to 8 Nm (71 in-lbs) with the inch-pound torque wrench.

Step 6: Remove the coil pack and plug wires

• Gently twist the coil pack side to side to loosen the rubber boots from the plugs.
• Pull the coil and attached wires straight out and up; it may feel snug, but do not yank hard.
• Set the coil on a clean rag so dirt does not get into the boots.

Step 7: Clean the spark plug wells

• Look down into the spark plug wells with a flashlight.
• Use compressed air to blow out dust and grit from around the plugs so debris does not fall into the cylinders.
• Wear safety glasses while using compressed air.

Step 8: Remove the first spark plug

• Install the 5/8" spark plug socket on a 6" extension and 3/8" ratchet.
• Slide the socket down onto the first spark plug and make sure it is fully seated.
• Turn counterclockwise (left) to loosen and remove the plug. If it feels very tight, apply steady, smooth pressure.
• Lift the plug out carefully; the spark plug socket’s rubber insert should hold it. If it drops, use the magnetic pickup tool.

Step 9: Remove the second spark plug for that cylinder

• The second plug for the same cylinder is next to the first in a separate hole.
• Repeat the same process with the 5/8" spark plug socket and extension to remove this second plug.
• Keep track so you know you have removed both plugs for this cylinder.

Step 10: Check and set spark plug gap

• Use the feeler gauge to measure the gap on each new plug.
• The typical spec for this engine is around 1.1 mm (0.043"). Confirm on the plug box or HowToo listing.
• Adjust gently if needed by slightly bending the ground strap using the gauge tool, not by prying on the center electrode.
• Gaps should match across all 16 plugs.

Step 11: Install the new spark plugs (first cylinder)

• Attach a new plug to the 5/8" spark plug socket and extension.
• Lower it into the plug well and start threading it by hand only, turning clockwise (right).
• Make sure it spins in easily with your fingers; if it binds, back it out and restart to avoid cross-threading.
• Once finger-tight, attach the foot-pound torque wrench to the extension and tighten to 20 Nm (15 ft-lbs).
• Repeat for the second plug in this cylinder: hand-thread first, then torque to 20 Nm (15 ft-lbs).
• Do not use anti-seize on these plugs unless the plug manufacturer specifically instructs it; most Hemi plugs are pre-coated.

Step 12: Prepare the coil boots

• Inspect the rubber boots on the coil and plug wires for cracks or carbon tracking (black burn marks).
• Wipe the inside of each boot with a clean rag.
• Apply a thin film of dielectric grease inside each boot; this helps sealing and future removal.

Step 13: Reinstall the coil pack for that cylinder

• Align the coil boots with the two new plugs and push them straight down until you feel them seat on the plugs.
• Install the two 10mm bolts by hand first to avoid cross-threading.
• Use the 10mm socket and 3/8" ratchet to snug them up, then torque to 8 Nm (71 in-lbs) with the inch-pound torque wrench.
• Reconnect the coil’s electrical connector until it clicks.

Step 14: Repeat for the remaining cylinders on this side

• Move to the next coil on the same side.
• For each coil/cylinder pair, repeat Steps 4 through 13:
  • Unplug coil connector.
  • Remove 10mm coil bolts.
  • Pull coil and plug wires.
  • Blow out wells.
  • Remove both old plugs.
  • Gap and install two new plugs to 20 Nm (15 ft-lbs).
  • Grease boots, reinstall coil, torque bolts to 8 Nm (71 in-lbs), reconnect connector.
• Mark each finished coil with tape so you don’t lose track.

Step 15: Do the opposite bank (other side of engine)

• Move to the other side of the engine; space may be tighter near the brake booster and other components.
• You may need the 3" extension and universal joint with the 5/8" spark plug socket to reach some plugs.
• Repeat the exact same process: one coil/cylinder at a time until all 8 cylinders (16 plugs) are completed.

Step 16: Final checks under the hood

• Confirm every coil connector is fully clicked in.
• Confirm all coil bolts are installed and torqued.
• Check that no tools, rags, or loose bolts are left on top of the engine.
• Reinstall the engine cover by aligning the grommets and pressing down until it snaps in.

Step 17: Reconnect the battery

• Reconnect the negative battery cable using a 10mm socket.
• Tighten the clamp snugly (do not over-tighten).
• If you have it, spray a light coat of battery terminal protector.

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✅ After Repair

• 🔑 Start the engine and let it idle. It may crank slightly longer the first start, but it should settle into a smooth idle.
• 👂 Listen for misfires (shaking or stumbling). If it runs rough, shut off and re-check every coil connector and wire.
• 💡 If the check engine light was on for misfires before, it may clear itself after a few drive cycles; if you have a scan tool, clear the codes now.
• 🚗 Take a short, gentle test drive. Accelerate smoothly; the engine should feel smoother and more responsive.
• 🔁 After the drive, recheck under the hood for anything loose and make sure no warning lights remain.

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💰 DIY vs Shop Cost

Shop Cost: $450–$700 (parts + labor)

DIY Cost: $100–$200 (parts only, depending on plug brand)

You Save: $350–$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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