How to replace Lexus spark plugs?

Replacing a Lexus spark plug is a straightforward job for many DIY enthusiasts. In short, you’ll remove each ignition coil, extract the old plug, fit a new OEM-type plug, and tighten to the manufacturer’s torque specification before testing the engine.

What you need to know before you begin

Spark plugs ignite the air-fuel mixture in each cylinder, and worn plugs can cause rough idle, reduced power, and lower fuel economy. Lexus engines commonly use a coil-on-plug design, where each cylinder has its own ignition coil mounted on the spark plug boot. Access, torque, and plug-gap specifications vary by model and engine type, so always confirm the exact service data for your car in the owner’s manual or service manual. If you’re not comfortable working around the engine, consider a professional service to avoid potential damage.

Tools and parts you'll need

Collecting the right tools and parts before you start helps prevent delays and protects the engine from debris or cross-threading.

• New spark plugs (OEM or equivalent based on your Lexus engine) – iridium or platinum types are common for modern Lexuses


• Spark plug socket (typically 5/8 inch) with a long extension and magnetic pickup


• Ratchet, swivels, and assorted extensions (6–12 inches commonly helpful)


• Torque wrench calibrated for ft-lbs (and a rough metric equivalent if you prefer)


• Dielectric grease for coil boots and connectors


• Flat-head or needle-nose pliers for prying or guiding, if needed


• Compressed air or a soft brush to keep debris out of plug wells


• Rags or a small container for old plugs


• Gloves and eye protection for safety


• Die-cast or OEM replacement parts compatible with your model; avoid non-OEM plugs that don’t meet Lexus heat-range specifications

Note: Do not rely on anti-seize on modern Lexus engines unless specifically directed by your manual. Many OEM plugs are designed to install without anti-seize, and using it can alter torque values or cause over-tightening.

Step-by-step replacement process

These steps provide a clear, model-agnostic workflow. Some details (like bolt sizes or exact coil layout) vary by engine, so consult your manual for model-specific nuances.

1. Park on a flat surface, set the parking brake, and disconnect the negative battery terminal to prevent any electrical shorts.


2. Allow the engine to cool completely to avoid burns and to ensure accurate torque readings.


3. Remove any engine covers or shrouds that obstruct access to the spark plugs.


4. Identify the ignition coils on the valve cover. If your engine uses coil-on-plug (COP), each cylinder’s coil sits directly over its spark plug.


5. Carefully disconnect the electrical connector on the coil. Some coils are held by a single retaining bolt; remove the bolt with the appropriate tool and gently lift the coil straight up to expose the plug.


6. Blow or wipe away any debris around the plug wells with compressed air or a clean brush to prevent dirt from entering the combustion chamber.


7. Attach the spark plug socket to the extension and ratchet. Gently loosen and remove the old spark plug, keeping the plug in a throwaway container to avoid contamination elsewhere in the engine.


8. Compare the old plug to the new one to verify correct heat range and type. If the plug is pre-gapped, skip gap adjustments unless your manual specifies otherwise; otherwise, gap the new plug to the recommended specification using a suitable gap tool.


9. Thread the new plug by hand into the cylinder head to avoid cross-threading. Once finger-tight, snug it with the spark plug wrench, then torque to the manufacturer’s specification using a torque wrench. Do not over-tighten; overtightening can strip the threads in aluminum heads.


10. Reinstall the ignition coil over the new plug, apply a small amount of dielectric grease to the inside of the coil boot if recommended, connect the electrical connector, and re-secure the coil with its mounting bolt to the specified torque.


11. Repeat steps 5–11 for each cylinder in the engine, keeping track of which coil belongs to which cylinder to ensure correct reassembly.


12. Once all plugs are replaced, reattach any engine covers, reconnect the battery, and start the engine to confirm a smooth idle and normal operation. If the check-engine light appears, use an OBD-II scanner to read codes and address any misfire concerns.


13. Perform a short test drive to ensure the engine runs cleanly and there are no unusual sounds or misfires. If everything seems fine, proceed with a final inspection for any loose hoses or connectors that may have shifted during the job.

With the steps complete, you should notice improved throttle response, smoother idle, and better overall engine performance compared with worn plugs.

Aftercare and maintenance considerations

After replacing spark plugs, consider these follow-up steps to maximize the benefit of the service and maintain engine health.

• Scan for codes if any misfires or pending codes persist; clear codes only after corrective action is confirmed


• Observe fuel economy and performance over the next several driving cycles to ensure proper seating of the plugs


• Schedule a maintenance check if you notice any persistent rough idle, stalling, or reduced power


• Keep the ignition system components clean and dry; avoid exposing the new plugs to moisture or contaminants during installation

Tip: If you’re unsure about any step or encounter unusual resistance, stop and consult a Lexus service specialist. A misstep in torque or installation can cause engine damage or misfires.

Model-specific notes for Lexus engines

Most newer Lexus models use coil-on-plug ignition with individual ignition coils per cylinder, which makes plug replacement a straightforward process—though access can vary. Some four- and six-cylinder layouts place a plug deeper in the cylinder head, requiring extra extensions or a longer reach tool. Always refer to your model’s service data for exact torque specs, plug gap, and any special instructions about torque-to-angle procedures or anti-seize recommendations. If your engine uses a direct-ignition coil arrangement, handle each coil with care to avoid damaging the boot or connector, and replace any worn coil boots if you notice cracks or moisture intrusion.

Summary

Replacing Lexus spark plugs is a practical DIY task when you have the right tools, the correct type of plugs, and the engine-specific torque and gap information. Plan ahead, work methodically cylinder by cylinder, and verify the result with a test drive and any necessary diagnostics. When done properly, the car should run more smoothly, efficiently, and with improved throttle response.

How often should you change spark plugs on a Lexus?

Lexus spark plug replacement intervals vary by model and spark plug type, but generally range from 60,000 to 100,000 miles. Newer models with iridium or titanium plugs typically have a longer interval, often around 100,000 miles or more, while some earlier models or specific engines may recommend replacement every 60,000 miles. Always check your vehicle's owner's manual or scheduled maintenance guide for the most accurate information. 
General guidelines

• Modern Lexus with iridium or titanium plugs: Replacement is often recommended every 100,000 miles. 
• Specific models: Some Lexus models, even newer ones, may have a 60,000-mile interval, so it's important to check the specific maintenance schedule. 
• Signs of worn plugs: Regardless of the interval, you may need to replace them sooner if you experience symptoms like engine misfires, reduced fuel efficiency, difficulty starting, or poor acceleration. 

How to find your specific interval

• Consult your owner's manual: This is the most reliable source for your vehicle's specific maintenance schedule. 
• Check your Scheduled Maintenance Guide: This document will provide detailed information on when components like spark plugs should be serviced. 
• Ask a certified technician: A Lexus technician can provide expert advice for your specific make and model. 

How much does it cost to replace spark plugs in a Lexus?

The cost to replace Lexus spark plugs can range from $400 to over $1,100, with an average around $400 to $700 at an independent shop. A major factor is how accessible the spark plugs are—some Lexus models, like certain IS and ES sedans, have spark plugs buried under components that add significant labor time and cost, potentially pushing the total well over $1,000. 
This video explains how to save money by replacing spark plugs yourself: 1mScrew This!YouTube · Sep 6, 2023
Cost breakdown

• Parts: 6 to 8 spark plugs, which can cost around $10 to $25 each depending on the material (e.g., iridium or platinum), plus any necessary gaskets or other parts. 
• Labor: The price is highly variable, depending on how long it takes to access the plugs. It can be as low as a few hours or several, pushing the cost up significantly for models with more complex engine designs. 
• Dealer vs. independent shop: Dealerships typically charge more, while independent shops can offer more competitive rates. You may find an independent shop willing to do the work for $100-$200 in labor if the spark plugs are easy to access. 
• Other factors: The final price will also depend on your location and the specific parts (like OEM vs. aftermarket) used. If the mechanic recommends replacing other parts, like coils, at the same time, this will also increase the total cost. 

What are signs of bad spark plugs?

Signs of bad spark plugs include rough idling, difficulty starting the engine, decreased fuel economy, and poor acceleration. You may also experience engine misfires, which can cause the vehicle to shake or hesitate, and the check engine light to illuminate. 
Performance issues

• Rough idling: The engine shakes or sputters when the car is stopped. 
• Engine misfires: The engine skips a beat, which can be felt as a hesitation or vibration. 
• Poor acceleration: The vehicle feels sluggish when you press the gas pedal. 
• Engine knocking: Unusual knocking or pinging sounds may come from the engine. 

Fuel and starting problems

• Poor fuel economy: You'll notice you need to fill up the gas tank more often. 
• Difficulty starting: The engine may crank for a longer time before starting. 

Visual and warning signs

• Check engine light: The light may come on, especially if the misfires are frequent. 
• Black exhaust smoke: The tailpipe might emit black smoke. 
• Visual inspection: When removed, a bad spark plug may show a worn electrode, a cracked insulator, or deposits of oil or fuel. 

Can I replace my spark plugs by myself?

You can absolutely do it yourself. Spark plugs are like the quintessential first job for an amateur auto enthusiast / DIY'er. Take it slow and follow the instructions, and you're good to go. I recommend getting a magnetic sparkplug socket. The ones with the little o-ring that grips the plug can be finicky.