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2020 RDX Rough Idle & Misfire - Spark Plugs or Coil Packs?

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Tom H. · rep 0 · May 22, 4:59 AM · 1 replies · solved · Question

Vehicle: 2020 Acura RDX Advance

My 2020 Acura RDX with the 2.0T engine just hit 65,000 miles, and I've started noticing a rough idle, especially when cold. The check engine light came on yesterday, and when I scanned it, I got a P0302 code, indicating a misfire on cylinder 2.

Could this just be the spark plugs needing replacement? I haven't changed them yet. Or is it more likely a coil pack issue? I've heard both can cause misfires.

What's the recommended service interval for spark plugs on these RDX models? Any tips for diagnosing whether it's the plug or the coil before I start buying parts?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 4:59 AM

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ClearTheCode admin answer:

It sounds like you're on the right track with diagnosing your 2020 Acura RDX's rough idle and P0302 misfire code. Both spark plugs and ignition coils are common culprits for misfires, especially around your mileage.

Here's how to approach it:

  1. Spark Plug Service Interval: For your 2.0T engine in the 2020 RDX, Acura generally recommends spark plug replacement around 60,000 to 105,000 miles, depending on driving conditions. At 65,000 miles, it's definitely within the range where spark plugs could be worn and causing issues.
  2. Diagnosing Plug vs. Coil:
    • Swap Test: The easiest way to differentiate between a bad spark plug and a bad coil pack is to perform a 'swap test'. Move the ignition coil from cylinder 2 to a different cylinder (e.g., cylinder 1 or 3). Clear the code, drive the car, and re-scan. If the misfire code moves to the new cylinder (e.g., P0301 or P0303), then the coil pack is faulty. If the code remains P0302, then the spark plug in cylinder 2 is likely the issue.
    • Visual Inspection: When you remove the spark plug from cylinder 2, inspect it for signs of wear, fouling (oil, carbon, or fuel deposits), or damage to the electrode.
  3. Replacement: If it's the spark plug, replace all four plugs with OEM-specified iridium plugs. If it's the coil pack, you can replace just the faulty one, though some owners prefer to replace them in pairs or all at once for preventative maintenance.

Causes of Misfires:

  • Worn Spark Plugs: Over time, the electrode gap widens, requiring more voltage to spark, leading to intermittent misfires.
  • Faulty Ignition Coil: Coils can fail due to heat, vibration, or age, leading to a weak or absent spark.
  • Fuel Injector Issues: Less common, but a clogged or failing fuel injector can also cause a misfire (though usually accompanied by other codes).
  • Compression Issues: In rare cases, low compression in a cylinder can cause misfires, but this is typically accompanied by more severe symptoms.

When to See a Shop:

  • If the swap test doesn't clearly identify the problem.
  • If you're uncomfortable working with ignition components.
  • If the misfire persists after replacing the suspected part, indicating a deeper issue.
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