🔧 Grand Cherokee - Ignition Coil Replacement

This repair replaces the ignition coils on your Grand Cherokee’s 5.7L HEMI V8. Ignition coils create the high-voltage spark that fires the spark plugs, and a weak coil can cause misfires, rough idle, flashing check engine light, or poor acceleration.

Difficulty Level: Beginner | Estimated Time: 1.5-2.5 hours

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⚠️ Safety & Precautions

• ⚠️ Work only with the engine completely cool to avoid burns from the cylinder heads and exhaust area.
• ⚠️ Disconnect the negative battery cable before unplugging ignition coils to reduce electrical risk and avoid accidental shorts.
• ⚠️ Do not pull on the coil wiring. Pull only on the connector body after releasing the lock tab.
• ⚠️ Keep dirt and debris away from the spark plug wells while the coils are removed.
• ⚠️ If the check engine light is flashing, avoid driving until the misfire is fixed because catalytic converter damage can occur.

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🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 8mm socket
• 1/4-inch drive ratchet
• 3/8-inch drive ratchet
• 3-inch extension
• 6-inch extension
• Torque wrench inch-pound range
• Flathead screwdriver
• Plastic trim tool
• Needle-nose pliers
• Compressed air nozzle
• OBD-II scan tool
• Safety glasses
• Nitrile gloves
• Fender cover

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Ignition coil - Qty: 1-8
• Dielectric grease - Qty: 1 tube

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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 completely before touching the coils.
• 🔋 Use a 10mm socket to disconnect the negative battery cable, then move the cable away from the battery post.
• 🧰 An OBD-II scan tool is a small plug-in reader used to identify which cylinder is misfiring, such as P0301 for cylinder 1.
• 📍 Cylinder numbering on the 5.7L HEMI: passenger side front-to-rear is 2-4-6-8; driver side front-to-rear is 1-3-5-7.
• 💡 Each cylinder has one coil-on-plug assembly. “Coil-on-plug” means the coil sits directly on top of the spark plug.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Read Misfire Codes

• Plug the OBD-II scan tool into the diagnostic port under the driver-side dashboard.
• Turn the ignition to RUN without starting the engine.
• Use the OBD-II scan tool to read stored codes.
• Match the code to the cylinder: P0301 means cylinder 1, P0302 means cylinder 2, and so on.
• If replacing all coils as maintenance, continue with all eight cylinders.
• Label cylinders before removing parts.

Step 2: Disconnect the Battery

• Open the hood and install the fender cover to protect the paint.
• Use a 10mm socket and 3/8-inch drive ratchet to loosen the negative battery terminal clamp.
• Lift the negative cable off the battery post and position it where it cannot spring back.

Step 3: Remove the Engine Cover

• Grip the engine cover with both hands and pull straight upward to release it from the rubber mounting grommets.
• If it feels stuck, use a plastic trim tool gently at the edge of the cover.
• Set the cover aside in a safe place.
• Pull upward, not sideways.

Step 4: Locate the Ignition Coils

• Find the rectangular ignition coils along the top outer edges of both cylinder heads.
• Each coil has an electrical connector and mounting fasteners.
• Use a compressed air nozzle to blow dirt away from the coil area before removal.
• Do not blow debris directly into open connectors.

Step 5: Disconnect the Coil Electrical Connector

• Put on safety glasses and nitrile gloves.
• Use a flathead screwdriver to gently unlock the connector safety tab if equipped.
• Press the release tab with your thumb or use needle-nose pliers carefully if access is tight.
• Pull the connector straight off the ignition coil by the plastic connector body.
• Do not pull on the wires.

Step 6: Remove the Ignition Coil Fasteners

• Use an 8mm socket, 3-inch extension, and 1/4-inch drive ratchet to remove the coil mounting bolts.
• Keep the bolts in order so they do not get lost.
• If rear coils are tight to access, use the 6-inch extension for a straighter angle.

Step 7: Remove the Old Ignition Coil

• Twist the ignition coil gently by hand to loosen the rubber boot from the spark plug.
• Pull the coil straight upward and out of the spark plug well.
• If it sticks, work it side-to-side by hand only. Do not pry against the cylinder head.
• Inspect the rubber boot for oil, carbon tracking, cracks, or white burn marks.
• Carbon tracking looks like pencil lines.

Step 8: Prepare the New Ignition Coil

• Compare the new ignition coil to the old one before installing it.
• Apply a small amount of dielectric grease inside the end of the rubber boot only.
• Dielectric grease is a silicone grease that helps seal out moisture and prevents the boot from sticking.
• Do not smear grease on the electrical connector pins.

Step 9: Install the New Ignition Coil

• Push the new ignition coil straight down over the spark plug until the boot seats fully.
• Start the mounting bolts by hand first to avoid cross-threading.
• Use an 8mm socket, 3-inch extension, and torque wrench inch-pound range to tighten the coil bolts.
• Torque to 8 Nm (71 in-lbs).
• Do not overtighten. These bolts thread into aluminum.

Step 10: Reconnect the Coil Connector

• Push the electrical connector onto the ignition coil until it clicks.
• If equipped, use your finger or a flathead screwdriver to slide the connector safety lock back into place.
• Gently tug on the connector body to confirm it is locked.

Step 11: Repeat for Additional Coils

• Repeat Steps 5-10 for each ignition coil being replaced.
• Use the 8mm socket, extensions, and torque wrench inch-pound range for each coil.
• Replace coils one at a time to avoid mixing up connectors.
• One-at-a-time prevents mistakes.

Step 12: Reinstall the Engine Cover

• Align the engine cover with the rubber mounting grommets.
• Press straight down by hand until it snaps into place.
• Do not use tools to force the cover on.

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 terminal clamp snugly.
• Do not overtighten the clamp because the battery post can be damaged.

Step 14: Clear Codes and Start the Engine

• Use the OBD-II scan tool to clear misfire codes.
• Start the engine and let it idle.
• Listen for smooth idle and watch for a check engine light.
• If the engine runs rough, shut it off and recheck the coil connector you serviced.

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✅ After Repair

• ✅ Let the engine idle for 2-3 minutes and confirm it runs smoothly.
• ✅ Take a short test drive with light acceleration first, then moderate acceleration if everything feels normal.
• ✅ Re-scan with the OBD-II scan tool after the test drive to confirm no misfire codes returned.
• ✅ If the same cylinder misfire returns, the spark plug, fuel injector, wiring, compression, or intake leak may need diagnosis.
• ✅ If battery disconnect caused clock or radio presets to reset, restore them through the Uconnect screen.

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💰 DIY vs Shop Cost

Shop Cost: $180-$850 depending on whether replacing one coil or all eight

DIY Cost: $35-$400 parts only depending on quantity and brand

You Save: $120-$450 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 0.7-1.8 hours.

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🎯 Ready to get started?

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