🔧 Durango - Spark Plug Replacement

Your Durango’s 6.4L uses 16 spark plugs (two per cylinder). Replacing them restores smooth running, strong power, 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 fully cool engine to avoid burns and damaged threads.
• ⚠️ Disconnect the negative battery cable using a 10mm wrench if you’re worried about accidentally cranking or shorting coils.
• ⚠️ Blow dirt away from plug wells before removing plugs so debris doesn’t fall into the cylinder.
• ⚠️ Do not use anti-seize on modern plated spark plugs unless the plug manufacturer specifically requires it.

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🔧 Required Tools

You'll need the following tools for this repair:

• Safety glasses
• Nitrile gloves
• 10mm socket
• 10mm wrench
• 3/8" ratchet
• 3/8" torque wrench (10–30 ft-lbs range)
• 5/8" spark plug socket
• 6" 3/8" extension
• 12" 3/8" extension
• 3/8" swivel universal joint
• Trim clip remover
• Compressed air blow gun
• Feeler gauge (wire style)
• Small flat screwdriver

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Spark plugs (correct spec for 6.4L) - Qty: 16
• Dielectric grease - Qty: 1

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📋 Before You Begin

• Park on level ground, set the parking brake, and let the engine cool completely.
• Remove jewelry/watches; you’ll be working near power wiring.
• If disconnecting the battery: use a 10mm wrench to remove the negative cable and isolate it so it can’t spring back.
• Plan to do one cylinder at a time so parts don’t get mixed up.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover and open up access

• Lift the engine cover straight up to release it from the rubber grommets.
• If the air intake tube or resonator box blocks access on a side, loosen clamps with a small flat screwdriver and remove fasteners with a 10mm socket, then move it aside.
• Take a quick photo before unplugging anything.

Step 2: Unplug and remove one ignition coil

• Pick one cylinder and stay on it until both plugs are done.
• Press the connector lock and unplug the coil electrical connector.
• Remove the coil hold-down bolt using a 10mm socket.
• Twist the coil boot slightly, then pull the coil straight up and out.
• Torque on install: Ignition coil bolt to 8 Nm (71 in-lbs)

Step 3: Clean the plug wells

• Use compressed air blow gun to blow out dirt from around the spark plug tubes/wells.
• If there’s oil in a plug well, stop and address the leak first (common cause is a seal/boot issue).

Step 4: Remove the spark plug(s) for that cylinder

• Use a 5/8" spark plug socket with a 6" extension and 3/8" ratchet to loosen and remove the plug.
• For the tighter plug on that cylinder, use a 12" extension and 3/8" swivel universal joint as needed to line up straight.
• Pull the plug out carefully so you don’t crack the ceramic.

Step 5: Check and prep the new plugs

• Verify you have the correct plugs (matching what came out).
• Check gap with a feeler gauge (wire style). If the plugs are iridium/platinum, do not pry on the fine tip; replace if the gap is off.
• Apply a tiny smear of dielectric grease inside the coil boot (this helps future removal and keeps moisture out).

Step 6: Install the new spark plug(s)

• Start the plug by hand using the 5/8" spark plug socket and extension only (no ratchet at first) to avoid cross-threading.
• Once it seats, tighten with a 3/8" torque wrench.
• Torque: Spark plug to 18 Nm (13 ft-lbs)
• If it doesn’t spin in easily, back out and re-start.

Step 7: Reinstall the coil and connector

• Push the coil straight down until it fully seats on the plug.
• Install the coil bolt using a 10mm socket, then finish with a 3/8" torque wrench.
• Torque: Ignition coil bolt to 8 Nm (71 in-lbs)
• Reconnect the coil electrical connector and make sure the lock clicks.

Step 8: Repeat for all cylinders (all 16 plugs)

• Move methodically cylinder-by-cylinder so you don’t miss the second plug on any cylinder.
• If rear cylinders are tight, use the 12" extension and 3/8" swivel universal joint to keep the socket straight.

Step 9: Reassemble intake parts and engine cover

• Reinstall any intake tubing/boxes removed using a 10mm socket and tighten clamps with a small flat screwdriver.
• Reinstall the engine cover by aligning the grommets and pushing straight down.
• If you disconnected the battery, reconnect the negative cable using a 10mm wrench.

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✅ After Repair

• Start the engine and let it idle for 30–60 seconds. It should be smooth with no flashing check engine light.
• Listen for ticking/hissing (could indicate a loose plug or unplugged connector).
• Road test gently, then do a couple of moderate accelerations. Recheck for any warning lights.
• If a check engine light appears, scan for misfire codes—most often a coil connector not fully seated.

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💰 DIY vs Shop Cost

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

DIY Cost: $120-$280 (parts only)

You Save: $330-$620 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.