🔧 Forester - Ignition Coil Replacement

Your Forester’s ignition coils sit on top of the engine and create the high-voltage spark for each cylinder. Replacing a weak coil can fix misfires, rough idle, flashing check-engine light, and loss of power.

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

Assumption: FA20DIT turbo layout with top-mount intercooler removal for access.

---

⚠️ Safety & Precautions

• ⚠️ Work on a cold engine; the turbo/intercooler area gets very hot.
• ⚠️ Disconnect the negative battery cable to prevent shorts and accidental cranking.
• ⚠️ Don’t pull on wiring; release connector locks to avoid broken tabs.
• ⚠️ Keep dirt out of spark plug tubes; blow out debris before removing coils.

---

🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 12mm socket
• 3/8" ratchet
• 6" extension for 3/8" ratchet
• Torque wrench (5–30 Nm range)
• Flat-blade screwdriver
• Hose clamp pliers
• Trim clip tool
• Pick tool
• Compressed air blow gun
• Shop rags
• Nitrile gloves
• Safety glasses

---

🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Ignition coil - Qty: 4 (replace as needed; best to match/set)
• Dielectric grease - Qty: 1
• Top-mount intercooler to throttle-body seal/gasket - Qty: 1
• Bypass valve gasket - Qty: 1

---

📋 Before You Begin

• Park on level ground, shift to Park, and set the parking brake.
• Open the hood and let the engine cool fully.
• Use a 10mm socket to disconnect the negative battery terminal and move it aside so it can’t spring back.
• Lay out coils in order (Cylinder 1–4) so you don’t mix parts during troubleshooting.

---

🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover (if equipped)

• Pull up firmly by hand, or remove fasteners using a trim clip tool if your cover uses clips.
• Set the cover aside.

Step 2: Remove the top-mount intercooler for access

• Loosen intercooler hose clamps using a flat-blade screwdriver.
• Remove intercooler bracket bolts using a 12mm socket with a 3/8" ratchet and 6" extension.
• Remove the bypass valve bolts using a 10mm socket.
• Carefully lift the intercooler up and out; wiggle gently to release hoses without tearing them.
• A pick tool helps stubborn hose edges.

Step 3: Blow out debris around each coil

• Use compressed air blow gun and safety glasses to blow dirt away from the coil area.
• This helps prevent grit from falling into the spark plug tube.

Step 4: Unplug the ignition coil electrical connector

• Press the connector lock tab and pull the connector straight off by hand.
• If the tab is stubborn, use a pick tool gently to lift the lock while you pull.
• Never pry hard on the connector housing.

Step 5: Remove the ignition coil

• Remove the coil hold-down bolt using a 10mm socket and 3/8" ratchet.
• Twist the coil slightly, then pull straight up to remove it from the spark plug tube.
• Wipe the tube opening area with shop rags if needed.

Step 6: Prep and install the new coil

• Apply a small dab of dielectric grease inside the rubber boot (this helps sealing and future removal).
• Push the new coil straight down until it fully seats on the spark plug.
• Install the hold-down bolt by hand first to avoid cross-threading.
• Tighten the coil bolt using a torque wrench (5–30 Nm range): Torque to 6.4 Nm (4.7 ft-lbs).

Step 7: Reconnect the coil connector

• Push the connector on until it clicks/locks.
• Repeat Steps 3–7 for the remaining coils.

Step 8: Reinstall the intercooler

• Install a new top-mount intercooler to throttle-body seal/gasket and bypass valve gasket if removed.
• Set the intercooler back in place, making sure the couplers are fully seated.
• Tighten bracket bolts using a 12mm socket and bypass valve bolts using a 10mm socket.
• Tighten hose clamps using a flat-blade screwdriver.
• Mis-seated hoses cause boost leaks and poor power.

Step 9: Reconnect the battery

• Reconnect the negative battery terminal using a 10mm socket.
• Make sure it’s fully seated and secure.

---

✅ After Repair

• Start the engine and let it idle for 2–3 minutes; it should run smooth with no shaking.
• Listen for hissing near the intercooler couplers (a sign of a boost/vacuum leak).
• Test drive gently, then do a few medium accelerations; verify no flashing check-engine light.
• If a check-engine light remains, scan for codes (misfire codes like P0301–P0304 can point to a different issue such as spark plugs or wiring).

---

💰 DIY vs Shop Cost

Shop Cost: $350-$750 (parts + labor)

DIY Cost: $160-$500 (parts only)

You Save: $190-$250 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.

---

🎯 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.