A Comprehensive Guide to Spark Plugs for the 2008-2012 Infiniti EX35
Keep your EX35's powerful V6 engine running at its peak by understanding and choosing the right spark plugs.
- For best performance and longevity, use NGK or Denso Iridium spark plugs, which are the OEM-equivalent brands.
- The recommended replacement interval is 105,000 miles, but symptoms like rough idle or poor MPG warrant an earlier inspection.
- Replacement is a difficult DIY job due to the need to remove the intake manifold to access some plugs; professional service is recommended for most owners.
- When replacing plugs, check for oil in the spark plug tubes, as this indicates a common valve cover gasket leak that should be fixed at the same time.
Symptoms of Failing Spark Plugs
When your spark plugs start to wear out, your EX35 will likely give you a few warning signs. Ignoring these can lead to worse fuel mileage and potential engine damage. Look out for:
- Rough Idling: The engine may shake or vibrate more than usual when stopped.
- Poor Acceleration: The car may feel sluggish or hesitant when you press the gas pedal.
- Reduced Fuel Economy: Worn plugs can cause a drop in gas mileage by as much as 30%.
- Engine Misfires: You might feel a hesitation or stumbling from the engine, often accompanied by a flashing Check Engine Light.
- Difficulty Starting: A weak spark can make it harder for the engine to turn over and start smoothly.
Check Engine Light
A common sign of a spark plug issue is a Check Engine Light. The most frequent codes are P0300 (Random Misfire) or codes P0301 through P0306, which indicate a misfire in a specific cylinder. A flashing Check Engine Light is serious and means you should have the vehicle checked immediately to prevent damage to the catalytic converter.
Choosing the Right Aftermarket Spark Plugs
Your Infiniti EX35 came from the factory with long-lasting Iridium-tipped spark plugs, and it's best to stick with this type for aftermarket replacements. While cheaper copper or platinum plugs are available, they won't last as long or perform as well in the high-energy ignition system of the VQ35HR engine. The original equipment manufacturer (OEM) is typically NGK or Denso.
Brand Tiers for Your EX35
Tier 1: Best Quality (OEM Equivalent)
- NGK: Widely considered the OEM supplier for Nissan/Infiniti, NGK Laser Iridium or Iridium IX plugs are a top choice. They are designed specifically for your engine and offer the best performance and longevity, often lasting up to 100,000 miles.
- Denso: Another excellent Japanese brand and OEM supplier, Denso Iridium plugs are also highly recommended for the EX35. They provide performance and durability on par with NGK.
Tier 2: Good Quality
- Bosch: Bosch offers high-quality Double Iridium spark plugs that are a solid choice for the EX35. While often associated with European cars, their iridium plugs are well-regarded and provide reliable performance.
Tier 3: Standard Quality
- Champion: Champion provides iridium plugs that meet the basic requirements for your engine. While functional, they are generally not considered to be in the same performance or longevity class as NGK or Denso for this specific vehicle.
A Note on Counterfeits
Be cautious when purchasing spark plugs from online marketplaces like Amazon or eBay, as counterfeit NGK and Denso plugs are common. Buying from a reputable auto parts store ensures you get genuine, high-quality parts.
Cost Comparison for Spark Plug Replacement
| Item | Cost Range |
|---|---|
| Set of 6 Aftermarket Iridium Spark Plugs (NGK, Denso, Bosch) | $60 - $180 |
| Shop Labor for Replacement | $220 - $322 |
| Total Professional Replacement | $280 - $502 |
Frequently Asked Questions (FAQ)
When should I replace the spark plugs on my EX35?
The recommended service interval for the original iridium spark plugs is 105,000 miles. However, if you experience any failure symptoms, you should inspect them sooner.
Is replacing the spark plugs a DIY job?
It can be, but it is challenging. The VQ35HR engine's design makes accessing the spark plugs, especially those near the firewall, difficult. The intake manifold and throttle bodies may need to be removed to reach all six plugs. This job is best for experienced DIY mechanics. For most owners, professional installation is recommended.
What is the correct spark plug gap for the EX35?
The recommended spark plug gap is 0.044 inches. Most quality iridium plugs come pre-gapped, and it is generally advised not to adjust them to avoid damaging the fine iridium tip.
Are there any recalls or known issues?
There are no specific recalls or Technical Service Bulletins (TSBs) from Infiniti for spark plugs on the 2008-2012 EX35. However, a common related issue is the valve cover gasket leaking oil into the spark plug tubes, which can cause a misfire. If you find oil on a spark plug when removing it, the valve cover gasket will also need to be replaced.
Technical Specifications
OEM Part Numbers: 22401-JK01D 22401-EW61C
Material: Iridium, Recommended Gap: 0.044 inches (1.1mm), Socket Size: 14mm
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The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
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