🔧 340i - Ignition Coil Replacement

Your ignition coils sit on top of the engine and send high-voltage spark to the spark plugs. Replacing weak or failed coils can fix misfires, rough idle, and flashing check-engine lights.

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

---

⚠️ Safety & Precautions

• ⚠️ Let the engine cool fully before starting; coils sit on hot metal.
• ⚠️ Keep the ignition OFF and the key/fob away from the car so it can’t auto-wake.
• ⚠️ Avoid pulling on wiring; only pull on connectors and the coil body.
• ⚠️ Battery disconnect is not strictly required, but it’s safer if you’re nervous around connectors.

---

🔧 Required Tools

You'll need the following tools for this repair:

• 8mm socket
• 10mm socket
• 1/4" drive ratchet
• 3" extension for 1/4" ratchet
• Trim removal tool
• Small flathead screwdriver
• Torque wrench (2-20 Nm range)
• Nitrile gloves
• Safety glasses

---

🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Ignition coil - Qty: 6
• Dielectric grease - 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 down completely.
• If disconnecting the battery: use a 10mm socket to remove the negative terminal and isolate it so it can’t spring back.

---

🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover

• Use a trim removal tool to gently lift up on the engine cover corners (it’s held by rubber grommets and pops upward).
• Lift the cover off and set it aside. Pull straight up, not sideways.

Step 2: Expose the coils (if any small covers are in the way)

• If your 340i has small plastic wire/channel covers over the coil area, remove their fasteners using an 8mm socket or 10mm socket (varies by cover).
• Set fasteners in a tray so nothing gets lost.

Step 3: Unplug the first coil connector

• At coil #1, locate the electrical connector lock (BMW connectors typically have a locking lever).
• Use a small flathead screwdriver only if needed to start the lock moving, then finish by hand.
• Rotate/flip the connector lock to release it, then pull the connector straight off.
• If it resists, re-check the lock position.

Step 4: Remove the coil

• Grab the coil body and pull straight upward to remove it.
• If it’s stuck, gently wiggle while pulling up by hand (don’t pry on the valve cover).
• A “coil” is the pencil-shaped unit that sits directly on the spark plug.

Step 5: Prepare the new coil

• Compare the new coil to the old one to ensure the connector and length match.
• Apply a tiny smear of dielectric grease inside the coil boot (the rubber end) using a gloved finger. This helps prevent moisture issues and makes future removal easier.

Step 6: Install the new coil

• Push the new coil straight down onto the spark plug until it fully seats (you’ll feel it “bottom out”).
• Reconnect the electrical plug and lock it by rotating/flipping the connector lock back into the fully locked position.

Step 7: Repeat for the remaining coils

• Repeat Steps 3–6 for coils #2 through #6, one at a time so you don’t mix up connectors.
• Work left-to-right to stay organized.

Step 8: Reinstall covers and engine cover

• Reinstall any plastic wire/channel covers using an 8mm socket or 10mm socket and a 1/4" drive ratchet.
• Torque to 8 Nm (71 in-lbs) for small plastic cover bolts (snug, not tight).
• Reinstall the engine cover by aligning the grommets and pressing straight down until it snaps into place.

Step 9: If you disconnected the battery, reconnect it

• Install the negative terminal using a 10mm socket.
• Torque to 5 Nm (44 in-lbs).

---

✅ 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 clear, or you can clear codes with a scan tool.
• Test drive for 10–15 minutes and re-check for any warning lights or rough running.
• If you still have a misfire, the next common item is spark plugs (often replaced with coils).

---

💰 DIY vs Shop Cost

Shop Cost: $350-$800 (parts + labor)

DIY Cost: $180-$450 (parts only)

You Save: $170-$350 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.

---

🎯 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.

Assumption: coil packs are the push-in style with locking-lever connectors (most 340i setups).