When should I replace spark plugs on my 4Runner?

The typical replacement interval for the 4Runner’s 4.0-liter V6 is about 120,000 miles under normal driving conditions.

That baseline can vary with plug type, driving style, and climate. Always refer to your owner’s manual for the exact recommendation for your model year, and have a mechanic confirm if you notice performance changes.

Understanding the recommended interval

For the 4Runner’s 4.0L V6, the official maintenance schedule generally lists spark plug replacement at roughly 120,000 miles for normal operation. Driving conditions or ignition components can shorten or extend that window, so it’s wise to assess your vehicle against real-world usage.

The timing can vary based on plug type and how you drive. Many 4Runner models use long-life iridium or platinum plugs, which supports a longer interval, but always verify the exact specification for your year and ignition setup in the manual or with a dealer.

Factors that can affect replacement timing include plug type, driving conditions, and overall engine health. If you regularly tow heavy loads, operate in dusty environments, make a lot of short trips, or drive in extreme heat or cold, you may need to pay closer attention to plug condition and consider replacement sooner rather than later.

• Normal driving: about 120,000 miles (190,000 km) for long-life iridium/platinum plugs commonly used in the 4.0L V6.


• Severe driving: towing, frequent short trips, dusty or hot climates, or heavy stop-and-go can lead to earlier wear; inspect and consider replacement sooner (often in the 60,000–100,000 mile range depending on usage).


• Always confirm the exact interval for your year and plug type in the owner’s manual or with a Toyota service advisor.

In short, follow the official schedule for your specific vehicle and monitor for signs of wear. If in doubt, a quick diagnostic check can determine whether replacement is due.

Signs your spark plugs may need replacement

Watch for these indicators of worn or failing plugs. If you notice any of these, have the ignition system inspected promptly to avoid further engine problems.

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If you observe these symptoms, schedule maintenance to determine whether the plugs, ignition coils, or related components are at fault and to prevent potential damage.

Replacement process overview

Replacing spark plugs on a 4Runner is a straightforward task for those with mechanical experience. If you’re unsure, a qualified technician can perform the job. Here is a general outline of the process.

1. Gather the correct spark plugs for your engine (iridium or platinum long-life type as specified by Toyota for the 4.0L V6), plus a ratchet, spark plug socket, extension, torque wrench, and anti-seize or lubricant only if recommended by the manual.


2. Disconnect the negative battery cable to prevent any electrical short or shock.


3. Remove the coil-on-plug assemblies to access each spark plug (one per cylinder) and carefully disconnect them from the coils.


4. Carefully thread out the old spark plugs with the proper socket, avoiding any sudden twisting to prevent thread damage in the cylinder head.


5. Inspect the cylinder bores and the plug wells, then check and gap the new plugs according to the manufacturer’s specification if gap adjustment is required for your plug type.


6. Install the new plugs to the recommended torque from the service manual, and reinstall the coil packs and wiring harnesses securely.


7. Reconnect the battery, start the engine, and monitor for smooth operation and absence of misfires. Clear any codes if needed and return the engine to normal idle.

Torque specifications and exact steps can vary by model year and ignition system. Always follow the Toyota service manual or a certified technician’s instructions for your specific 4Runner.

Summary

For most 4Runner models with the 4.0L V6, spark plugs are typically replaced around 120,000 miles under normal driving. Severe driving conditions, plug type, and maintenance history can shorten or extend that interval. Look for signs of wear such as rough idle, misfires, reduced fuel economy, or hard starts, and have the plugs inspected or replaced as needed. If you’re not comfortable performing the replacement yourself, a professional technician can handle the job, ensuring proper torque and ignition system integrity. Regular adherence to the owner’s manual will help keep your 4Runner running smoothly for years to come.

What year to stay away from a Toyota 4Runner?

The Toyota 4Runner years to avoid are generally 2003-2005 due to severe frame rust and engine issues, and earlier models like 1988-1995 (specifically with the 3.0L V6) due to head gasket failures. Other problematic years include 2001-2002 for rust and 2010-2011 for airbag defects. 
This video discusses the best and worst years for the Toyota 4Runner, including common problems to watch out for: 59scar PROblemsYouTube · Oct 29, 2024
Problematic model years by generation 

• First Generation (1984-1989): Avoid 1988-1989 models with the 3.0L V6 engine due to potential head gasket failures. 
• Second Generation (1990-1995): Avoid 1990-1995 models with the 3.0L V6 engine for the same head gasket issues. 
• Third Generation (1996-2002): Avoid 2001-2002 models due to reports of severe frame rust and suspension problems. 
• Fourth Generation (2003-2009): This is the most problematic generation. 
  • 2003-2005: These years are notorious for severe frame rust, and some 2003-2004 models are also associated with head gasket failure and dashboard cracks. The 2004 model is often cited as one of the worst due to a combination of rust, ABS problems, and poor rear impact safety ratings. 
• Fifth Generation (2010-present): Avoid 2010-2011 models due to dangerous airbag defects. 

Key issues to be aware of

• Frame and body rust: A significant problem, particularly for the 2003-2005 models, can lead to expensive repairs or a complete vehicle write-off. 
• Engine issues: The 3.0L V6 engine in the second-generation 4Runner is prone to head gasket failure. 
• Airbag defects: A recall affected the 2010-2011 models due to faulty airbags. 
• Dashboard cracks: This was an ongoing issue in some models, including the 2004. 
• Suspension and brake problems: The 2001-2002 models had suspension issues, while the 2004 had a high number of complaints about the ABS not working properly. 

How much does it cost to replace spark plugs in a 4Runner?

The cost to replace the spark plugs in a Toyota 4Runner ranges from about $400 to $800, with dealer service typically being more expensive than an independent mechanic. The price depends on labor rates, whether you use OEM or aftermarket parts, and the specific year and model of your 4Runner. 
Cost breakdown

• Dealer: Expect to pay between $405 and $800. This includes higher labor rates and genuine OEM parts, which can also be more expensive. 
• Independent mechanic: Costs can range from approximately $327 to $475. These shops may use aftermarket parts, which are often less expensive than OEM parts. 
• Parts: Spark plugs themselves can cost anywhere from $3 to $50 or more per plug, depending on the brand and type. For a 4Runner, they can be around $10 to $27 per plug. 

Factors that influence the cost

• Labor rates: Labor is a significant portion of the total cost, often higher at dealerships. 
• Parts: The price of spark plugs varies by brand and quality. OEM parts from the dealership will be more expensive than aftermarket options. 
• Vehicle Year and Model: Older models might have slightly lower part costs, while newer V6 and V8 models can have different labor estimates. 
• Engine Access: Some engines, like the 4.0L V6, have spark plugs that are more difficult to access, requiring removal of the intake manifold and other parts, which increases labor time and cost. 

DIY vs. Professional

• DIY: If you're comfortable with car maintenance, you can do the job yourself and save a significant amount of money, potentially for under $100 in parts and tools. 
• Professional: If you're not comfortable doing the work yourself, professional installation is recommended. It ensures the job is done correctly and safely, avoiding potential damage to your engine. 

How often does Toyota recommend changing spark plugs?

Toyota recommends changing spark plugs every 60,000 to 100,000 miles, but this varies by model, and your owner's manual is the best source for the exact schedule. Newer models with iridium or platinum plugs generally have longer intervals (often 100,000+ miles), while older ones with standard copper plugs may require replacement every 30,000-50,000 miles. 
Replacement intervals by plug type

• Copper: Typically every 30,000 miles.
• Platinum: Around 60,000 miles or more.
• Iridium: Can last 100,000 to 120,000 miles or more. 

Signs that your spark plugs need replacing sooner

• Rough idling: The engine may feel like it's sputtering or misfiring. 
• Difficulty starting: The engine may take longer to turn over when you start the car. 
• Poor fuel economy: You notice a drop in your vehicle's gas mileage. 
• Weak acceleration: The car feels like it lacks power or has slow acceleration. 

Important considerations

• Check your owner's manual: Always consult your vehicle's owner's manual for the precise maintenance schedule, as it is the most accurate guide for your specific model. 
• Consider your driving conditions: Severe driving, such as frequent short trips, stop-and-go traffic, or towing, can shorten the life of spark plugs and may require more frequent replacement. 

How often should spark plugs be changed on a 4Runner?

Toyota recommends replacing 4Runner spark plugs every 120,000 miles. This is a long-life interval, and it's also a good idea to have them inspected sooner and to check your owner's manual for the most accurate information for your specific model year. 
You can watch this video to learn how to replace the spark plugs on a Toyota 4Runner: 51sT4R GarageYouTube · Feb 10, 2024

• Official recommendation: Toyota's recommended interval for most newer 4Runner models is 120,000 miles. 
• Owner's manual: Always consult your owner's manual to find the exact replacement schedule for your vehicle. 
• Inspection: It is recommended to have spark plugs inspected at the first sign of engine trouble, such as poor acceleration, rough idling, or trouble starting. 
• Potential signs of wear:
  • Difficulty starting the engine 
  • Poor or sluggish acceleration 
  • Engine misfires 
  • Increased fuel consumption