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Rough Idle and Misfires on 2019 QX60 - Time for Spark Plugs?

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Laura J. · rep 0 · May 22, 5:08 AM · 1 replies · solved · Question

Vehicle: 2019 Infiniti QX60 Luxe

My 2019 Infiniti QX60, with about 85,000 miles, has developed a noticeable rough idle lately. Sometimes, it feels like it's stumbling a bit under light acceleration. The check engine light came on briefly a few times, but then went off. I scanned it with a basic OBD reader and got a pending P030X code (P0301, P0303, etc.) for multiple cylinder misfires.

Could this be a sign that the spark plugs need replacing? What's the recommended interval for the VQ35DD engine in the QX60? Is this a DIY-friendly job or should I take it to a mechanic?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 5:08 AM

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ClearTheCode admin answer:

  1. Likely Cause: Spark Plugs: Your symptoms – rough idle, stumbling, and especially the P030X (P0301, P0303, P0305, etc. indicating cylinder misfires) OBD codes – strongly suggest that your spark plugs are a primary suspect. Over time, spark plugs wear down, leading to a weaker spark, incomplete combustion, and misfires.
  2. Recommended Interval: For the VQ35DD engine in your 2019 QX60, Infiniti typically recommends spark plug replacement between 60,000 and 105,000 miles, depending on the specific plug type and driving conditions. At 85,000 miles, you are well within the range where replacement is due.
  3. Why It's Important: Worn spark plugs can lead to:
    • Reduced fuel economy
    • Loss of engine power
    • Increased emissions
    • Catalytic converter damage (due to unburnt fuel entering the exhaust)
  4. DIY Considerations: Replacing spark plugs on the QX60's VQ35DD engine can be a DIY job for those with moderate mechanical experience. You'll need a spark plug socket, torque wrench, and potentially an extension. The rear bank of cylinders can be a bit more challenging to access due to the intake manifold, but it's generally manageable. Ensure you use the correct OEM-specified iridium spark plugs (e.g., NGK Laser Iridium).
  5. When to See a Shop: If you're uncomfortable working on your engine, or if the misfires persist after replacing the plugs, it's best to consult a professional. Persistent misfires could indicate other issues such as faulty ignition coils, fuel injectors, or even compression problems, which require more advanced diagnostics.
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