🔧 WRX - Ignition Coil Replacement

Your WRX uses one ignition coil per cylinder to create spark. When a coil gets weak or fails, you can get misfires, rough idle, flashing check engine light, and loss of power.

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

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⚠️ Safety & Precautions

• ⚠️ Let the engine cool fully before starting (hot turbo/intercooler parts burn fast).
• ⚠️ Disconnect the negative battery cable to prevent accidental short circuits.
• ⚠️ Do not pull on wiring; release connectors by the lock tab.
• ⚠️ Keep dirt out of the spark plug wells; debris can cause misfires.

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🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 12mm socket
• 3/8" ratchet
• 3" extension (3/8" drive)
• 6" extension (3/8" drive)
• Torque wrench (3/8" drive, 5–30 ft-lbs range)
• Flat trim tool
• Needle-nose pliers
• Pick tool
• Shop rags
• Flashlight
• Nitrile gloves
• Safety glasses

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Ignition coil - Qty: 1-4
• Dielectric grease - Qty: 1

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📋 Before You Begin

• Park on level ground, set the parking brake, and open the hood.
• Let the engine cool completely.
• Disconnect the battery negative terminal using a 10mm socket and tuck it aside so it can’t spring back.
• Lay out rags to cover open areas so you don’t drop bolts into the engine bay.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the top-mount intercooler (for access)

• Use a flat trim tool to remove any plastic clips securing the intercooler duct/shroud (if equipped).
• Use a 10mm socket to loosen the worm clamps on the intercooler couplers.
• Disconnect the bypass valve return hose using needle-nose pliers (squeeze the spring clamp and slide it back).
• Use a 12mm socket and 3/8" ratchet to remove the intercooler mounting bolts.
• Wiggle the intercooler free and lift it out carefully; set it on a clean rag. Take your time; hoses can stick.

Step 2: Unplug one ignition coil connector

• Pick one coil to start with (doing one at a time helps prevent mixing anything up).
• Use a flashlight to locate the coil connector lock tab.
• Use a pick tool to gently help lift the lock tab if it’s stubborn, then pull the connector straight off.

Step 3: Remove the ignition coil hold-down bolt

• Use a 10mm socket, 3/8" ratchet, and a 3" extension to remove the coil hold-down bolt.
• Place the bolt in a tray or pocket so it doesn’t get lost.

Step 4: Remove the ignition coil

• Grip the coil body and twist it slightly left/right to break the seal.
• Pull the coil straight out of the spark plug well.
• Use shop rags to wipe any dust around the coil opening (do not push debris inside).

Step 5: Prep and install the new ignition coil

• Apply a tiny dab of dielectric grease inside the rubber boot (this helps prevent moisture and makes future removal easier).
• Push the coil straight down until it fully seats on the spark plug.
• Install the hold-down bolt by hand first (prevents cross-threading).
• Use a torque wrench (3/8" drive, 5–30 ft-lbs range) to tighten the bolt: Torque to 6.4 Nm (4.7 ft-lbs). A torque wrench is a tool that tightens bolts to the correct force so you don’t strip threads.

Step 6: Reconnect the coil electrical connector

• Push the connector on until it clicks.
• Gently tug it to confirm it’s locked.

Step 7: Repeat for the remaining coils

• Repeat Steps 2–6 for the other cylinders.
• Use a 6" extension (3/8" drive) as needed for tighter angles.

Step 8: Reinstall the top-mount intercooler

• Set the intercooler back into position, making sure the couplers align evenly.
• Reinstall the mounting bolts using a 12mm socket and 3/8" ratchet, then snug them evenly.
• Reconnect the bypass valve return hose using needle-nose pliers.
• Tighten the intercooler coupler clamps using a 10mm socket. Even clamp placement helps prevent boost leaks.
• Reinstall any ducting/clips removed using a flat trim tool.

Step 9: Reconnect the battery

• Reconnect the negative battery cable using a 10mm socket.

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✅ After Repair

• Start the engine and let it idle for 2–3 minutes; it should run smoothly.
• Listen for hissing near the intercooler couplers (a hiss can mean a boost/vacuum leak from a loose clamp).
• If you had a flashing check engine light before, drive gently at first and confirm the light stays off.
• If the check engine light returns, stop and re-check each coil connector and intercooler clamps.

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💰 DIY vs Shop Cost

Shop Cost: $250-$650 (parts + labor)

DIY Cost: $70-$400 (parts only)

You Save: $180-$250+ by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 1.5-2.5 hours.

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🎯 Ready to get started?

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