🔧 RX350 - Ignition Coil Replacement

Ignition coils turn battery voltage into the high voltage needed to fire your spark plugs. Replacing a bad coil can fix misfires, rough idle, flashing check-engine light, and poor acceleration.

Difficulty Level: Intermediate | Estimated Time: 1.0-3.0 hours

Assumption: V6 rear-bank coils require upper intake removal.

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⚠️ Safety & Precautions

• ⚠️ Let the engine cool fully before starting (hot intake and exhaust parts burn).
• ⚠️ Disconnect the negative battery cable to prevent accidental shorts and to protect electronics.
• ⚠️ Do not pull on wiring—release connector locks first to avoid broken terminals.
• ⚠️ Keep bolts and tools out of the intake runners; dropping hardware inside can cause engine damage.

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🔧 Required Tools

You'll need the following tools for this repair:

• Safety glasses
• Nitrile gloves
• 10mm socket
• 10mm deep socket
• Ratchet
• 3/8" drive torque wrench (5–30 Nm range)
• 1/4" drive ratchet
• 6" socket extension
• 12" socket extension
• Universal joint adapter
• Flathead screwdriver
• Trim clip removal tool
• Needle-nose pliers
• Magnetic pickup tool
• Shop flashlight
• Shop towels

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Ignition coil - Qty: 1-6
• Upper intake manifold gasket set - Qty: 1
• Throttle body gasket - Qty: 1
• Dielectric grease - Qty: 1

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📋 Before You Begin

• Park on level ground and set the parking brake.
• Open the hood and let the engine cool completely.
• Use a 10mm socket to disconnect the negative battery cable and isolate it so it cannot spring back.
• Label any vacuum hoses or connectors you remove with tape 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 grommets (rubber push-in mounts).
• Set it aside where it won’t get stepped on.

Step 2: Remove the air intake duct (to make room)

• Use a flathead screwdriver to loosen the hose clamps on the intake duct.
• Unclip or unplug any small hoses/ports using needle-nose pliers (move clamps back first).
• Lift the duct out and set it aside.

Step 3: Replace front-bank ignition coils (easy access)

• Locate the coils on the front cylinder bank (closest to the radiator).
• Press the connector lock tab and unplug the coil connector (use a flathead screwdriver gently if the tab is stubborn).
• Use a 10mm socket with a ratchet to remove the coil hold-down bolt.
• Twist the coil slightly, then pull straight up to remove it from the spark plug tube.
• Put a tiny smear of dielectric grease inside the new coil boot (the rubber tip). Dielectric grease is a non-conductive grease that helps prevent moisture and sticking.
• Push the new coil straight down until it fully seats.
• Reinstall the hold-down bolt and Torque to 9 Nm (80 in-lbs).
• Reconnect the electrical connector until it clicks.

Step 4: Gain access to rear-bank ignition coils (upper intake removal)

• Unplug any intake-area connectors and move harnesses out of the way (use a trim clip removal tool for plastic clips).
• Disconnect vacuum hoses from the upper intake using needle-nose pliers to slide clamps back.
• Use a 10mm socket, extensions, and a universal joint adapter to remove the upper intake manifold bolts/nuts.
• Lift the upper intake manifold straight up and off.
• Cover the exposed intake ports with clean shop towels immediately.

Step 5: Replace rear-bank ignition coils

• With the rear bank exposed, unplug each coil connector (press tab and pull).
• Use a 10mm socket to remove each coil hold-down bolt.
• Remove the coil by twisting slightly and pulling straight up.
• Apply a small amount of dielectric grease inside each new coil boot.
• Install the new coil and reinstall the bolt.
• Torque to 9 Nm (80 in-lbs) for each coil bolt.
• Reconnect each coil electrical connector until it clicks.

Step 6: Reinstall the upper intake manifold with new gaskets

• Remove the shop towels from the intake ports and confirm nothing fell in.
• Install the new upper intake manifold gaskets onto the manifold.
• Set the manifold in place carefully without pinching any wiring.
• Hand-start all bolts/nuts to avoid cross-threading.
• Use a 10mm socket to snug them evenly in a crisscross pattern.
• Tip: Tighten in stages for even sealing.
• Torque to 21 Nm (15 ft-lbs) for upper intake fasteners.

Step 7: Reinstall intake ducting and engine cover

• Reinstall the intake duct and tighten clamps using a flathead screwdriver.
• Reconnect any hoses and electrical connectors you removed.
• Press the engine cover back onto its grommets until it seats.

Step 8: Reconnect the battery

• Reconnect the negative battery cable using a 10mm socket.
• Make sure the terminal is snug and does not rotate by hand.

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✅ After Repair

• Start the engine and let it idle for 2–3 minutes. It should run smooth with no shaking.
• Listen for hissing (vacuum leak sound) around the upper intake area.
• If the check-engine light was on, clear codes after the repair (or it may clear after a few drive cycles if the issue is fixed).
• Test drive 10–15 minutes and recheck for warning lights.

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💰 DIY vs Shop Cost

Shop Cost: $350-$950 (parts + labor)

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

You Save: $290-$470 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 1-3 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.