🔧 Durango - Spark Plug Replacement

On your Durango’s 3.6L engine, the spark plugs wear over time and can cause misfires, rough idle, poor fuel economy, and hard starts. This job involves removing the ignition coils (the “coil packs” that sit on top of each plug) and swapping the plugs one cylinder at a time so nothing gets mixed up.

Difficulty Level: Intermediate | Estimated Time: 1.5-3.0 hours

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⚠️ Safety & Precautions

• ⚠️ Work on a cold engine to avoid burns and to protect aluminum threads in the cylinder heads.
• ⚠️ Disconnect the negative battery terminal to prevent accidental shorts while unplugging coils.
• ⚠️ Keep dirt out of the spark plug holes; debris can fall into the cylinder and cause damage.
• ⚠️ Do not over-tighten spark plugs; the cylinder head is aluminum and threads can strip.

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🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 8mm socket
• 1/4" drive ratchet
• 3/8" drive ratchet
• 3/8" drive torque wrench (10–30 Nm range)
• 6" extension (3/8" drive)
• 12" extension (3/8" drive)
• 5/8" spark plug socket (rubber insert or magnetic)
• Trim clip removal tool
• Small flathead screwdriver
• Compressed air blow gun
• Feeler gauge (0.043" blade)
• Dielectric grease
• Shop rags
• Nitrile gloves
• Safety glasses
• 10mm wrench

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Spark plugs (iridium, correct fit for 3.6L) - Qty: 6
• Upper intake/throttle body air tube clamp (optional, if damaged) - Qty: 1

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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 (at least 1 hour if it was hot).
• Use a 10mm wrench to disconnect the negative battery terminal and tuck it aside so it can’t spring back.
• Do one cylinder at a time to avoid mix-ups.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover (if equipped)

• Grab the cover firmly and pull upward to pop it off the mounting grommets.
• Set it aside where it won’t get stepped on.

Step 2: Create working room at the top of the engine

• Loosen the air intake tube clamps using an 8mm socket (or a small flathead screwdriver if it’s a worm-gear clamp).
• Unclip/remove any attached hoses or clips using a trim clip removal tool.
• Move the intake tube/resonator out of the way as needed for access.

Step 3: Unplug and remove one ignition coil

• Pick one cylinder to start with (front bank is usually easiest).
• Release the electrical connector lock with a small flathead screwdriver, then unplug the coil connector.
• Remove the coil hold-down bolt using a 10mm socket.
• Twist the coil slightly and pull it straight up to remove it.
• An ignition coil is the “stick” that snaps onto the plug.

Step 4: Clean around the spark plug well

• Use compressed air blow gun to blow dirt out of the spark plug “well” (the tube the coil came out of).
• Wipe the area with shop rags so nothing falls inside when the plug comes out.

Step 5: Remove the old spark plug

• Install the 5/8" spark plug socket with a 6" extension (use the 12" extension if needed).
• Use a 3/8" drive ratchet to loosen and remove the spark plug.
• Lift it out carefully so you don’t drop debris into the hole.

Step 6: Check and prep the new spark plug

• Check the gap using a feeler gauge (0.043" blade); many iridium plugs come pre-gapped, but verify.
• Do not apply anti-seize unless the plug manufacturer specifically requires it (most modern plated plugs do not).
• Apply a tiny smear of dielectric grease inside the coil boot (dielectric grease is a non-conductive grease that helps prevent moisture and makes future removal easier).

Step 7: Install the new spark plug

• Thread the new plug in by hand first using the 5/8" spark plug socket and extension (no ratchet) to prevent cross-threading.
• Once it seats, tighten with a 3/8" drive torque wrench: Torque to 13 Nm (115 in-lbs).

Step 8: Reinstall the ignition coil

• Push the coil straight down until it fully seats on the plug.
• Install the coil bolt using a 10mm socket, then tighten with a 3/8" drive torque wrench: Torque to 9 Nm (80 in-lbs).
• Reconnect the coil electrical connector until it clicks and locks.

Step 9: Repeat for the remaining 5 cylinders

• Repeat Steps 3–8 one cylinder at a time.
• Use the 12" extension and a steady hand for the tighter rear cylinders.
• If access is tight, remove only what blocks your hands.

Step 10: Reinstall the intake parts and engine cover

• Reinstall the intake tube/resonator and tighten clamps with an 8mm socket.
• Reinstall any clips/hoses you removed using a trim clip removal tool.
• Press the engine cover back into place.

Step 11: Reconnect the battery

• Reconnect the negative battery terminal using a 10mm wrench.

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✅ After Repair

• Start the engine and let it idle for 1–2 minutes; it should run smooth with no shaking.
• Listen for a hissing sound (could indicate an intake tube not seated) and recheck clamps with an 8mm socket.
• If the check engine light comes on or it runs rough, recheck each coil connector is fully clicked in.
• Road test for 10 minutes, then recheck for any loose clamps or forgotten tools.

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💰 DIY vs Shop Cost

Shop Cost: $350-$650 (parts + labor)

DIY Cost: $60-$140 (parts only)

You Save: $210-$590 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 1.5-3.0 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.