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2020 Accord 2.0T rough idle and misfires, CEL on

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Chris P. · rep 0 · May 22, 2:42 AM · 1 replies · solved · Question

Vehicle: 2020 Honda Accord Sport 2.0T

My 2020 Honda Accord Sport 2.0T has developed a really rough idle, and I can feel it misfiring, especially when cold. The check engine light came on and stayed on. I haven't had a chance to get the codes read yet, but it's definitely noticeable.

The car has around 50,000 miles. It feels like the engine is shaking more than usual, and sometimes there's a slight hesitation when accelerating.

Could this be a spark plug issue, or something more serious like a fuel injector problem? Any advice on what to check first before I take it to a mechanic?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 2:42 AM

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ClearTheCode admin answer:

A rough idle and misfires with a persistent Check Engine Light (CEL) on your 2020 Honda Accord Sport 2.0T indicates a specific cylinder or cylinders are not firing correctly. Here are the most common causes:

  1. Spark Plugs: Worn, fouled, or incorrectly gapped spark plugs are a very common cause of misfires. At 50,000 miles, it's a good time to inspect or replace them, especially if they haven't been done before.
  2. Ignition Coils: A failing ignition coil for one or more cylinders will prevent the spark plug from firing, leading to a misfire. These can sometimes fail intermittently.
  3. Fuel Injectors: Clogged or faulty fuel injectors (especially with direct injection engines) can prevent adequate fuel delivery to a cylinder, causing a misfire. Carbon buildup on the injector tips is a possibility.
  4. Vacuum Leaks: A vacuum leak in the intake system can cause unmetered air to enter the engine, leading to a lean condition and rough idle/misfires.
  5. Engine Carbon Buildup: Direct injection engines like your 2.0T can accumulate carbon deposits on the intake valves, which can disrupt airflow and cause misfires, particularly at idle.

Common OBD-II Codes: When you get the codes read, you'll likely see P0301, P0302, P0303, P0304 (indicating a misfire in cylinder 1, 2, 3, or 4 respectively), or P0300 (random/multiple cylinder misfire).

When to See a Shop: It's crucial to get the CEL codes read as soon as possible. This will tell you which cylinder(s) are misfiring, narrowing down the diagnostic process significantly. A professional technician can:

  • Read and interpret the diagnostic trouble codes.
  • Perform a cylinder power balance test.
  • Inspect spark plugs and test ignition coils.
  • Check fuel pressure and injector operation.
  • Look for vacuum leaks.

Driving with a persistent misfire can damage the catalytic converter, so prompt attention is recommended.

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