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2016 IS 350 F Sport Rough Idle & Misfire - P0301 Code

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Mike T. · rep 0 · May 25, 3:24 AM · 1 replies · solved · Question

Vehicle: 2016 Lexus IS 350 F Sport

Hello Lexus community,

I'm experiencing a worrying issue with my 2016 Lexus IS 350 F Sport. For the past few days, the car has been idling very roughly, almost like it's shaking. When I'm driving, especially at lower speeds or under light acceleration, it feels like it's misfiring. The check engine light came on and is now solid.

I managed to get a scan, and it's showing a P0301 code, which indicates a misfire in cylinder 1. I'm not sure if this is a simple spark plug issue, an ignition coil, or something more serious like an injector problem. The car has about 85,000 miles on it.

What's the most common cause for a P0301 on these engines? Should I try replacing the spark plug and coil pack on cylinder 1 myself, or is it better to take it straight to a mechanic? Any advice would be greatly appreciated!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 3:24 AM

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ClearTheCode admin answer:

The P0301 code on your 2016 Lexus IS 350 F Sport, indicating a misfire in cylinder 1, is a common diagnostic trouble code. It means the Engine Control Unit (ECU) has detected that cylinder 1 is not contributing power as it should. Addressing this promptly is important to prevent further damage to the catalytic converter.

Here are the most common causes and diagnostic steps:

  1. Ignition System:

    • Spark Plug: The most frequent culprit. Spark plugs wear out over time. If your plugs haven't been replaced recently (typically every 60k-100k miles, depending on type), a fouled or worn plug in cylinder 1 is a strong possibility.
    • Ignition Coil: The coil pack for cylinder 1 could be failing. A common diagnostic trick is to swap the coil pack from cylinder 1 with a known good cylinder (e.g., cylinder 3). If the misfire code then moves to the new cylinder (e.g., P0303), you've identified a faulty coil pack.

  2. Fuel System:

    • Fuel Injector: A clogged, dirty, or failing fuel injector for cylinder 1 can prevent proper fuel delivery, leading to a misfire. This is less common than ignition issues but definitely a possibility, especially with higher mileage.
    • Fuel Pressure: While less likely to affect only one cylinder, overall low fuel pressure could exacerbate an issue in a particular injector.

  3. Engine Mechanical:

    • Low Compression: In rare cases, a mechanical issue like a burnt valve, worn piston rings, or a head gasket leak could cause low compression in cylinder 1, leading to a misfire. This is typically diagnosed with a compression test or leak-down test.

What you can do:

  • Inspect Spark Plug: If you're comfortable, remove the spark plug from cylinder 1 and inspect its condition. Look for signs of fouling, damage, or excessive wear.
  • Swap Coil Pack: This is a relatively easy DIY step to confirm if the coil pack is the issue, as described above.

When to see a shop:

If swapping the coil pack doesn't move the misfire, or if you're not comfortable performing these checks yourself, it's best to take your Lexus to a professional. They can perform more advanced diagnostics, including:

  • Fuel injector flow tests.
  • Compression and leak-down tests.
  • Using an oscilloscope to check ignition coil primary and secondary waveforms.

Early diagnosis and repair will prevent potential damage to your catalytic converter, which can be very costly to replace.

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