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2016 Q60 3.0t Misfire & Check Engine Light - Spark Plugs or Coils?

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Mike T. · rep 0 · May 25, 3:50 AM · 1 replies · solved · Question

Vehicle: 2016 Infiniti Q60 3.0t Premium

Hey guys,

I've got a 2016 Infiniti Q60 3.0t Premium, just hit 80,000 miles. Lately, I've noticed a rough idle, especially when cold, and a slight loss of power under acceleration. The check engine light came on yesterday, and when I scanned it, I got P0301 and P0303, indicating misfires on cylinders 1 and 3.

I'm thinking it's either spark plugs or ignition coils. Given the mileage, what's more likely? Is this a DIY job for someone with moderate experience, or should I just bite the bullet and take it to the dealership or an independent shop? Any specific parts recommendations for the VR30DDTT engine?

Thanks for the help!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 3:50 AM

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Hello Mike T.,

It sounds like you're on the right track with your diagnosis for your 2016 Infiniti Q60 3.0t Premium. Misfire codes P0301 and P0303 (Cylinder 1 Misfire Detected, Cylinder 3 Misfire Detected) are classic indicators of issues with the ignition system, specifically spark plugs or ignition coils.

Here's a breakdown of what to consider:

  1. Common Causes:
    • Spark Plugs: At 80,000 miles, your original spark plugs are definitely at the end of their service life, if not past it. Infiniti typically recommends spark plug replacement for the VR30DDTT engine around 60,000 miles for optimal performance. Worn plugs can lead to weak spark, causing misfires.
    • Ignition Coils: While coils can fail, it's less common for multiple coils to fail simultaneously unless they're all original and aged. However, a failing coil can certainly cause a misfire on its cylinder. Sometimes, a weak coil will cause a misfire, and the worn spark plug exacerbates the issue.
    • Other Potential Causes (Less Likely Given Your Codes): Fuel injectors (clogged or faulty), vacuum leaks, or compression issues. However, with specific misfire codes, ignition components are the primary suspect.
  2. Diagnosis Steps:
    • Swap Test: To confirm if it's a coil, you can swap the ignition coil from cylinder 1 to, say, cylinder 5 (a cylinder not currently misfiring). Clear the codes, drive the car, and re-scan. If the misfire code moves to P0305, then the coil is faulty. Repeat for cylinder 3. If the misfire stays on P0301 and P0303, the issue is more likely the spark plugs or something else specific to those cylinders.
    • Inspect Plugs: When you pull the plugs, inspect them for wear, oil fouling, or carbon buildup.
  3. DIY vs. Shop: Replacing spark plugs on the VR30DDTT engine can be a moderately challenging DIY job. The engine bay is somewhat cramped, and accessing the rear bank (cylinders 1, 3, 5) requires removing some components (like the intake manifold on the passenger side for cylinder 1 and 3). If you have moderate experience, the right tools (torque wrench, various extensions, swivel sockets), and patience, it's doable. However, if you're not comfortable, an independent shop or dealership will have the specialized tools and experience.
  4. Parts Recommendations:
    • Spark Plugs: Always use OEM (Nissan/Infiniti) or equivalent NGK Laser Iridium spark plugs, which are specifically designed for the VR30DDTT engine. The part number is typically DILKAR8A8.
    • Ignition Coils: If you determine a coil is bad, replace it with an OEM Hitachi coil (Hitachi is the OEM supplier for Nissan/Infiniti) or a reputable aftermarket brand that meets OEM specifications.

When to See a Shop:

  • If you're not confident in performing the intake manifold removal or dealing with the tight spaces.
  • If the misfires persist after replacing the spark plugs and/or coils.
  • If you suspect other issues like fuel injectors or compression problems, which require more advanced diagnostic tools and expertise.
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