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2020 Lexus ES 350 Rough Idle and Check Engine Light - Misfire Codes?

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Mike T. · rep 0 · May 22, 4:40 AM · 1 replies · solved · Question

Vehicle: 2020 Lexus ES 350 Luxury

Hello Lexus community, I'm having a persistent problem with my 2020 Lexus ES 350. Recently, the car started idling very roughly, almost like it's shaking, especially when I'm stopped at a light. It's not constant, but it's noticeable and concerning.

To make matters worse, the check engine light came on a couple of days ago. I managed to get the codes read at an auto parts store, and it's showing P0301 and P0300. I believe those are misfire codes for cylinder 1 and a random/multiple misfire.

What could be causing these misfires in a relatively new car? I'm worried about potential damage. Any advice on what I should check first or what the common culprits are for this model year?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 4:40 AM

0

ClearTheCode admin answer:

Experiencing a rough idle and misfire codes (P0301 and P0300) in your 2020 Lexus ES 350 indicates an issue with the combustion process in one or more cylinders. While it's a newer vehicle, several components can fail prematurely or be affected by fuel quality or environmental factors.

Common Causes for Misfires (P0301, P0300):

  1. Ignition System Issues:
    • Spark Plugs: Worn, fouled, or incorrectly gapped spark plugs can lead to misfires. Even in newer cars, a defective plug can occur.
    • Ignition Coils: A failing ignition coil for cylinder 1 (P0301) would directly cause a misfire. A failing coil can also contribute to random misfires (P0300).
  2. Fuel System Issues:
    • Fuel Injector: A clogged, dirty, or faulty fuel injector for cylinder 1 would prevent proper fuel delivery, causing a misfire. This can also lead to P0300 if other cylinders are affected or if the overall fuel pressure is compromised.
    • Low Fuel Pressure: A failing fuel pump or clogged fuel filter could lead to insufficient fuel pressure, causing multiple cylinders to misfire.
  3. Air/Vacuum Leaks: Unmetered air entering the engine due to a vacuum leak (e.g., cracked hose, faulty PCV valve, intake manifold gasket) can lean out the air-fuel mixture, leading to misfires.
  4. Compression Issues: While less common in newer vehicles, low compression in cylinder 1 (due to valve issues, head gasket, or piston rings) would cause a misfire. This is usually a more severe mechanical problem.
  5. Sensor Malfunctions: A faulty Mass Air Flow (MAF) sensor or Oxygen (O2) sensor can send incorrect data to the Engine Control Unit (ECU), leading to an improper air-fuel mixture and subsequent misfires.

What to Do:

  1. Don't Ignore It: Continuing to drive with a misfire can damage the catalytic converter due to unburnt fuel entering the exhaust system.
  2. Professional Diagnosis: A qualified technician should perform a thorough diagnosis. They will typically:
    • Confirm the DTCs (P0301, P0300).
    • Inspect spark plugs and ignition coils, potentially swapping them between cylinders to see if the misfire moves.
    • Check fuel injector pulse and spray pattern.
    • Perform a compression test or leak-down test if mechanical issues are suspected.
    • Check for vacuum leaks using a smoke machine.
    • Monitor live data from MAF and O2 sensors.

When to See a Shop:

As soon as possible. The check engine light indicates an active problem that needs attention. Driving with a persistent misfire can lead to more expensive repairs down the line, especially to emissions components like the catalytic converter.

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