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2020 G70 3.3T Rough Idle & Misfire - CEL On (P0302)

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Christine P. · rep 0 · May 22, 6:16 AM · 1 replies · solved · Question

Vehicle: 2020 Genesis G70 3.3T Sport

Hey everyone, I'm having an issue with my 2020 Genesis G70 3.3T Sport. Recently, I've noticed a rough idle, especially when cold, and the check engine light came on. It feels like there's a slight hesitation or stumble when accelerating lightly.

I pulled the codes with my OBD scanner, and it's showing P0302, indicating a misfire on cylinder 2. I haven't done any major engine work recently, just regular oil changes. The car has about 60,000 miles on it.

Has anyone else experienced this with their G70? What was the fix? I'm hoping it's something simple like a spark plug or coil pack, but I'm open to suggestions before I take it to the dealer.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 6:16 AM

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ClearTheCode admin answer:

  1. Initial Diagnostics: A P0302 code specifically points to a misfire on cylinder 2. This is a good starting point for troubleshooting.

  2. Common Causes for P0302:

    • Worn Spark Plug: The most frequent culprit. Spark plugs degrade over time, leading to inefficient combustion in that cylinder.
    • Faulty Ignition Coil: If the spark plug is in good condition, the ignition coil for cylinder 2 might be failing. This component is responsible for delivering the high voltage needed to ignite the fuel-air mixture.
    • Clogged or Defective Fuel Injector: A fuel injector that isn't spraying correctly or is clogged can cause a lean condition and subsequent misfire in cylinder 2.
    • Vacuum Leak: While less common for a single-cylinder misfire, a localized vacuum leak could affect the fuel-air mixture specifically for cylinder 2.
    • Engine Compression Issues: In rarer cases, low compression in cylinder 2 due to issues like worn piston rings or valve problems could be the cause.
    • Carbon Buildup: Direct injection engines like the 3.3T are susceptible to carbon buildup on the intake valves, which can restrict airflow and lead to misfires, particularly at higher mileage.

  3. Troubleshooting Steps You Can Try:

    • Swap Components: A common diagnostic technique is to swap the spark plug from cylinder 2 with a spark plug from a known good cylinder (e.g., cylinder 4). If the misfire code then moves to the new cylinder (e.g., P0304), you've identified a faulty spark plug. If not, swap the ignition coil from cylinder 2 with a known good one. If the code moves, the coil is bad.
    • Inspect Wiring: Visually check the wiring harness and connector for the cylinder 2 ignition coil and fuel injector for any signs of damage or corrosion.

  4. When to See a Shop:

    • If you're not comfortable performing the diagnostic swaps yourself, or if they don't resolve the issue.
    • If further diagnostics are needed, such as fuel pressure tests, injector flow tests, or a compression test, as these require specialized tools and expertise.
    • If the misfire is severe, causing significant shaking, a noticeable loss of power, or if the check engine light is flashing (indicating a severe misfire that could damage the catalytic converter), it's crucial to get it to a shop immediately. Continuing to drive with a severe misfire can lead to costly repairs.
    • A Genesis dealership or a reputable independent shop specializing in Korean luxury vehicles will have the specific diagnostic equipment and experience with the 3.3T engine to accurately diagnose and repair the issue.
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