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2018 Q50 3.0t Rough Idle and Misfire - CEL On

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Sarah K. · rep 0 · May 22, 5:04 AM · 1 replies · solved · Question

Vehicle: 2018 Infiniti Q50 3.0t Red Sport

Hey everyone,

I'm having some trouble with my 2018 Infiniti Q50 3.0t Red Sport. Lately, it's developed a really rough idle, especially when I first start it up in the morning or after it's been sitting for a bit. It feels like it's shaking more than usual, and sometimes I even get a slight hesitation when accelerating from a stop.

The check engine light came on a few days ago, and I'm a bit worried. I haven't noticed any significant loss of power, but the rough idle is definitely concerning. Has anyone else experienced this with their VR30DDTT engine?

Any ideas on what could be causing this? I'm hoping it's something relatively simple before I have to take it to the dealership. Thanks for any advice!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 5:04 AM

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ClearTheCode admin answer:

It sounds like your 2018 Infiniti Q50 3.0t Red Sport is experiencing a common issue related to engine misfires, which can manifest as a rough idle and trigger the Check Engine Light (CEL). The VR30DDTT engine, while robust, can sometimes develop these symptoms.

Here's a breakdown of potential causes and steps:

  1. Check for OBD-II Codes:

    • The first step is to get the diagnostic trouble codes (DTCs) read. A rough idle and CEL often point to misfire codes like P0300 (Random/Multiple Cylinder Misfire Detected) or specific cylinder misfire codes (P0301 for cylinder 1, P0302 for cylinder 2, etc.).
    • Other related codes might include P0171/P0174 (System Too Lean) or P0420/P0430 (Catalyst System Efficiency Below Threshold), which can sometimes be secondary to misfires.

  2. Common Causes for Misfires in VR30DDTT:

    • Spark Plugs: Worn or fouled spark plugs are a very common culprit. The VR30DDTT engine can be hard on plugs, especially if tuned or driven aggressively.
    • Ignition Coils: A failing ignition coil on one or more cylinders will directly cause misfires.
    • Fuel Injectors: Clogged or faulty fuel injectors can lead to an improper air/fuel mixture, causing misfires.
    • Vacuum Leaks: Leaks in the intake system can introduce unmetered air, leading to a lean condition and misfires.
    • PCV System Issues: Problems with the Positive Crankcase Ventilation (PCV) system can also affect engine idle and cause misfires.
    • Carbon Buildup: Direct injection engines like the VR30DDTT are prone to carbon buildup on intake valves, which can restrict airflow and cause misfires, particularly at idle.

  3. When to See a Shop:

    • If you have access to an OBD-II scanner, reading the codes can give you a good starting point. However, diagnosing misfires can sometimes require more advanced tools and expertise.
    • If the CEL is flashing, this indicates a severe misfire that could be damaging the catalytic converter. In this case, it's crucial to stop driving and have the vehicle towed to a reputable shop or Infiniti dealership immediately.
    • Even if the light is solid, persistent rough idling and misfires should be addressed promptly to prevent further engine or emissions system damage. A qualified technician can perform a comprehensive diagnosis, including spark plug inspection, coil pack testing, fuel pressure checks, and potentially a compression test or smoke test for vacuum leaks.
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