🔧 MDX - Ignition Coil Replacement

Your MDX uses one ignition coil per cylinder (6 total). Replacing a bad coil can fix misfires, rough idle, and flashing check-engine lights. The front-bank coils are easy to reach; the rear-bank coils require removing the upper intake plenum to access them.

Difficulty Level: Intermediate | Estimated Time: 1.5-3.5 hours

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⚠️ Safety & Precautions

• ⚠️ Work on a cool engine; coils sit near hot components.
• ⚠️ Disconnect the negative battery terminal to prevent accidental shorts.
• ⚠️ Keep dirt out of the intake; cover openings with clean rags.
• ⚠️ If the check-engine light is flashing, avoid driving until fixed (can damage the catalytic converters).

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🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 12mm socket
• 1/4" drive ratchet
• 3/8" drive ratchet
• 3" extension (1/4" drive)
• 6" extension (3/8" drive)
• Torque wrench (5–30 ft-lbs range)
• Flathead screwdriver
• Needle-nose pliers
• Trim clip removal tool
• Shop flashlight
• Masking tape and marker
• OBD2 scan tool
• Nitrile gloves
• Safety glasses

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Ignition coil - Qty: 1-6
• Upper intake plenum gasket set - Qty: 1 (recommended if removing plenum)
• Throttle body gasket - Qty: 1 (recommended if throttle body is removed)
• Dielectric grease - Qty: 1 (helps seal coil boots; non-conductive grease)

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📋 Before You Begin

• 🅿️ Park on level ground and set the parking brake.
• 🔌 Use a 10mm socket to disconnect the negative battery terminal and isolate it.
• 🏷️ Use masking tape to label any hoses/connectors you remove so they go back to the same spot.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover

• Pull up on the plastic engine cover to release the rubber grommets (no tools), or remove any retaining fasteners using a 10mm socket if equipped.
• Set the cover aside.

Step 2: Decide what you’re replacing (front bank vs rear bank)

• Front bank (radiator side): coils are usually accessible once the cover is off.
• Rear bank (firewall side): you’ll remove the upper intake plenum (the top aluminum intake section that feeds air into the engine).
• Tip: If only one coil is bad, replace that one.

Step 3: Replace front-bank ignition coils (if applicable)

• Unplug the coil electrical connector by pressing the lock tab and pulling it off by hand.
• Remove the coil hold-down bolt using a 10mm socket.
• Twist the coil slightly and pull it straight up to remove it.
• Put a tiny smear of dielectric grease inside the new coil boot (the rubber sleeve) by hand.
• Install the new coil fully onto the spark plug.
• Reinstall the hold-down bolt using a 10mm socket and torque wrench: Torque to 12 N·m (9 ft-lbs).
• Reconnect the electrical connector until it clicks.

Step 4: Remove the air intake tube (for rear-bank access)

• Loosen the hose clamps using a flathead screwdriver.
• Disconnect any small breather/vacuum hoses using needle-nose pliers (move the clamp back, then pull the hose off).
• Lift the intake tube out and set it aside.

Step 5: Disconnect plenum-related connectors and hoses

• Unplug the throttle body electrical connector by hand.
• Disconnect vacuum/PCV hoses from the plenum using needle-nose pliers as needed.
• Label each hose/connector with masking tape.

Step 6: Remove the upper intake plenum (rear-bank access)

• Remove the plenum mounting bolts/nuts using a 12mm socket, ratchet, and extensions.
• Carefully lift the plenum up and off. If it’s stuck, gently wiggle it free—do not pry hard on sealing surfaces.
• Immediately cover the exposed intake openings with clean rags.
• Remove the old plenum gaskets and install the new ones (dry; no sealant unless the gasket kit specifically says so).

Step 7: Replace rear-bank ignition coils

• Unplug each coil connector by hand (press lock tab, then pull).
• Remove each coil hold-down bolt using a 10mm socket.
• Twist and pull each coil straight up to remove.
• Apply a small smear of dielectric grease inside each new coil boot.
• Install the new coils, then reinstall the hold-down bolts using a torque wrench: Torque to 12 N·m (9 ft-lbs).
• Reconnect coil connectors until they click.

Step 8: Reinstall the upper intake plenum

• Remove rags from the intake openings.
• Set the plenum in place, making sure gaskets stay aligned.
• Start all bolts/nuts by hand first (prevents cross-threading).
• Tighten evenly using a 12mm socket and torque wrench: Torque to 22 N·m (16 ft-lbs).
• Reconnect all hoses and electrical connectors you labeled.

Step 9: Reinstall the air intake tube and engine cover

• Reinstall the intake tube and tighten hose clamps using a flathead screwdriver.
• Reinstall any breather hoses and clamps using needle-nose pliers.
• Reinstall the engine cover (push into grommets, or use a 10mm socket if it has fasteners).

Step 10: Reconnect battery and clear codes

• Reconnect the negative battery terminal using a 10mm socket.
• Use an OBD2 scan tool to clear misfire/ignition codes.

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✅ After Repair

• 🔎 Start the engine and let it idle for 2–3 minutes; it should run smoothly.
• 🔎 Check for vacuum leaks: listen for hissing around the plenum and intake tube.
• 🧪 Test drive 10–15 minutes; re-scan with the OBD2 scan tool to confirm no misfire counts/codes returned.

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💰 DIY vs Shop Cost

Shop Cost: $350-$900 (parts + labor)

DIY Cost: $60-$480 (parts only)

You Save: $290-$420 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 1.5-3.5 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.