🔧 GLA - Ignition Coil Replacement

Your GLA’s ignition coils sit on top of the spark plugs and create the high voltage that fires the engine. When a coil fails, you can get misfires, rough idle, flashing check engine light, and loss of power.

Difficulty Level: Beginner | Estimated Time: 0.5-1.5 hours

Assumption: Stock 2.0L turbo (M270) with coil-on-plug setup.

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⚠️ Safety & Precautions

• ⚠️ Let the engine cool fully; coils sit near hot parts.
• ⚠️ Keep keys away from the car while unplugging coils to prevent wake-ups.
• ⚠️ Disconnect the negative battery terminal if you’ll be tugging hard on wiring.
• ⚠️ Do not pull on wires—only on the connector body.

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🔧 Required Tools

You'll need the following tools for this repair:

• 1/4" ratchet
• 3" extension (1/4")
• E10 external Torx socket
• Torque wrench (2-25 Nm range)
• Small flat trim tool
• Pick tool
• 10mm socket
• Battery terminal wrench (10mm)
• Nitrile gloves
• Safety glasses
• Shop light

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Ignition coil - Qty: 4
• Dielectric grease - 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.
• If disconnecting the battery: use a 10mm socket to remove the negative terminal and isolate it so it can’t spring back.
• Work clean—dirt falling into spark plug tubes can cause misfires.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover

• Grab the engine cover at the corners and pull upward firmly to pop it off its rubber grommets (press-in mounts).
• Use a shop light to identify the 4 coils lined up on top of the engine.

Step 2: Unplug one ignition coil (do one coil at a time)

• Locate the coil electrical connector on that coil.
• Use a small flat trim tool or pick tool to lift the connector lock (a small safety tab that prevents unplugging).
• Pull the connector straight off by the plastic housing (not the wires).
• One-at-a-time prevents mixing connectors.

Step 3: Remove the coil hold-down bolt

• Use a E10 external Torx socket with a 1/4" ratchet and 3" extension to remove the coil bolt.
• Set the bolt aside where it won’t fall into the engine bay.

Step 4: Pull the ignition coil out

• Twist the coil slightly left-right to break the seal, then pull straight up.
• If it’s stuck, keep twisting while pulling—don’t pry hard against plastic parts.
• Look down the spark plug tube with the shop light for oil or water. Oil can mean a valve cover leak that should be fixed.

Step 5: Prep and install the new ignition coil

• Apply a tiny smear of dielectric grease inside the rubber boot of the new coil (this helps prevent moisture and makes future removal easier).
• Push the new coil straight down until it fully seats on the spark plug.

Step 6: Reinstall and torque the coil bolt

• Start the bolt by hand to avoid cross-threading.
• Use a torque wrench (2-25 Nm range) with a E10 external Torx socket to tighten the bolt: Torque to 8 Nm (71 in-lbs).

Step 7: Reconnect the electrical connector

• Push the connector on until it clicks.
• Re-engage the connector lock (make sure it’s fully seated).

Step 8: Repeat for the other 3 coils

• Repeat Steps 2–7 for each remaining coil.

Step 9: Reinstall the engine cover

• Line up the cover with the mounting points and press down firmly at each corner until it snaps into place.
• If you disconnected the battery, reconnect the negative terminal using a 10mm socket.

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✅ After Repair

• Start the engine and let it idle for 1-2 minutes. It should run smooth with no shaking.
• If the check engine light was on, it may take a few drive cycles to go out; a scan tool can clear codes immediately (optional).
• Test drive 10-15 minutes. Recheck for any misfire feel under light acceleration.
• If you still have a misfire, the next common items are spark plugs or a wiring/connector issue.

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💰 DIY vs Shop Cost

Shop Cost: $400-$750 (parts + labor)

DIY Cost: $120-$320 (parts only)

You Save: $280-$430 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 0.8-1.2 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.