🔧 Challenger - Spark Plug Replacement

Your Challenger’s 6.4L HEMI uses 16 spark plugs (two per cylinder). Replacing them restores smooth idle, strong acceleration, and helps prevent misfires under load.

Difficulty Level: Intermediate | Estimated Time: 2.0-4.0 hours

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⚠️ Safety & Precautions

• 🧯 Work on a completely cool engine; hot aluminum threads can strip.
• 🧤 Disconnect the negative battery cable to prevent accidental shorting.
• 👓 Keep dirt out of the spark plug holes; debris can damage the cylinder.
• 🔥 Never pull on the wiring; unplug connectors by the lock tab.

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🔧 Required Tools

You'll need the following tools for this repair:

• Safety glasses
• Nitrile gloves
• 10mm socket
• 3/8" drive ratchet
• 3/8" drive torque wrench (5–30 ft-lbs range)
• 5/8" spark plug socket
• 3/8" drive extension set (3" and 6")
• 3/8" universal joint adapter
• Small flathead screwdriver
• Compressed air blow gun
• Feeler gauge (inch)
• Magnetic pickup tool
• Flashlight

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Spark plugs (6.4L HEMI, correct heat range) - Qty: 16
• Dielectric grease - Qty: 1

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📋 Before You Begin

• 🅿️ Park on level ground, transmission in neutral, parking brake set.
• 🧊 Let the engine cool fully (at least 1–2 hours after driving).
• 🔋 Open the trunk and disconnect the battery negative cable using a 10mm socket.
• 🏷️ Optional but helpful: label coil connectors by cylinder so nothing gets mixed up.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover (if equipped)

• Lift up firmly at the corners to pop it off (no tools usually needed).
• Use a flashlight to locate the ignition coils (one coil per cylinder).

Step 2: Unplug one coil at a time

• Press the connector lock tab and pull the connector straight off. Use a small flathead screwdriver only if the lock tab is stubborn.
• Do one cylinder at a time to avoid mix-ups.

Step 3: Remove the coil

• Remove the coil retaining bolt using a 10mm socket and 3/8" ratchet.
• Twist the coil boot slightly, then pull the coil straight up and out.
• Set the coil aside where it won’t get dirty.
• When reinstalling later: Torque to 8 Nm (71 in-lbs).

Step 4: Blow out the spark plug wells

• Use the compressed air blow gun to blow debris away from the spark plug hole before removing the plug.
• This prevents grit from falling into the cylinder.

Step 5: Remove the spark plugs (two per cylinder)

• Use a 5/8" spark plug socket (a socket with a rubber insert that grips the plug), plus a 3" or 6" extension and 3/8" ratchet.
• If access is tight, add a 3/8" universal joint adapter.
• Turn counterclockwise to remove. If a plug feels stuck, stop and work it gently back and forth.
• Use a magnetic pickup tool if a plug starts to slip while lifting it out.

Step 6: Check and set the plug gap (only if needed)

• Use a feeler gauge (inch) to verify the gap matches the spec for the plug set you purchased.
• If they are “pre-gapped,” don’t force-adjust unless one is clearly off.

Step 7: Install the new spark plugs by hand first

• Place the new plug in the 5/8" spark plug socket and carefully start the threads by hand using the extension only (no ratchet at first).
• If it doesn’t thread in smoothly, back it out and retry—don’t force it.
• Tighten with a 3/8" drive torque wrench: Torque to 17 Nm (13 ft-lbs).

Step 8: Reinstall coils and connectors

• Put a small dab of dielectric grease inside the end of each coil boot (this helps prevent moisture and eases future removal).
• Push the coil straight down until it seats.
• Install the coil bolt using a 10mm socket, then Torque to 8 Nm (71 in-lbs) with a torque wrench.
• Reconnect the coil electrical connector until it clicks.

Step 9: Repeat for all cylinders

• Replace all plugs across the engine: 16 total (two per cylinder).
• Cylinder layout reference (helpful when labeling): passenger side front-to-rear 1-3-5-7, driver side front-to-rear 2-4-6-8.

Step 10: Reconnect battery and reinstall engine cover

• Reconnect the negative battery cable using a 10mm socket.
• Press the engine cover back into place.

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✅ After Repair

• 🔍 Start the engine and listen for a smooth idle (no shaking/misfire).
• 🚗 Take a short test drive and verify acceleration is smooth under load.
• 🛠️ If you have a check engine light after the job, scan for codes—an unplugged coil connector is the most common cause.
• 👃 If you smell fuel or hear a “puffing” sound, shut it off and re-check plug torque and coil seating.

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💰 DIY vs Shop Cost

Shop Cost: $450-$900 (parts + labor)

DIY Cost: $140-$320 (parts only)

You Save: $310-$580 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?

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