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2017 Camry Rough Idle & Misfire Codes - Time for new spark plugs?

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David L. · rep 0 · May 22, 2:20 AM · 1 replies · solved · Question

Vehicle: 2017 Toyota Camry SE 2.5L

My 2017 Toyota Camry SE, 2.5L engine, just hit 105,000 miles, and lately, it's been running a bit rough. I've noticed a slight hesitation and a rough idle, especially when starting cold. The 'Check Engine' light came on, and when I scanned it, I got codes P0301 and P0303.

These are misfire codes for cylinders 1 and 3, right? Could this be a sign that it's time to replace the spark plugs? What kind of plugs should I use, and is this a job I can tackle myself, or should I take it to a mechanic?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 2:20 AM

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ClearTheCode admin answer:

Yes, you're absolutely right! OBD-II codes P0301 and P0303 indicate a misfire detected in cylinder 1 and cylinder 3, respectively. At 105,000 miles, especially with a rough idle and misfire codes, spark plugs are a very strong candidate for the cause.

Causes of Misfires at High Mileage:

  1. Worn Spark Plugs: The electrodes on spark plugs wear down over time, increasing the gap and requiring more voltage to fire, leading to weak or no spark.
  2. Fouled Plugs: Carbon buildup or oil/coolant contamination can prevent the plug from sparking correctly.
  3. Worn Ignition Coils: While less common than plugs, ignition coils can also degrade, especially if they're working harder to compensate for worn plugs.
  4. Fuel Delivery Issues: Clogged fuel injectors can also cause misfires, though less likely to be isolated to specific cylinders without other symptoms.

Spark Plug Replacement for Your 2017 Camry 2.5L:

  • Recommended Interval: Toyota typically recommends spark plug replacement for your engine around 120,000 miles, but symptoms like yours often warrant an earlier change.
  • Spark Plug Type: Your Camry requires iridium-tipped spark plugs. It's crucial to use the exact OEM-specified plugs (e.g., Denso or NGK) to ensure proper performance and longevity. Do not use copper or platinum plugs, as they are not designed for your engine's ignition system.
  • DIY Feasibility: Replacing spark plugs on the 2.5L engine is generally a straightforward DIY task. You'll need a spark plug socket, ratchet, torque wrench, and possibly a universal joint or extension. Ensure the engine is cool before starting. It's also a good idea to inspect or replace the ignition coils if they show signs of cracking or wear, and apply a small amount of dielectric grease to the coil boot.

When to See a Shop:

  • If replacing the spark plugs and inspecting coils doesn't resolve the misfire codes.
  • If you're uncomfortable working with engine components or don't have the necessary tools.
  • If the misfires are accompanied by other severe symptoms like engine knocking, significant power loss, or smoke from the exhaust, as these could indicate more serious engine issues.
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