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2018 Q50 Red Sport Misfire and Rough Idle - Any Ideas?

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Chris P. · rep 0 · May 24, 2:47 PM · 1 replies · solved · Question

Vehicle: 2018 Infiniti Q50 3.0t Red Sport

Hey everyone,

I've got a bit of a head-scratcher with my 2018 Infiniti Q50 3.0t Red Sport. Lately, it's been running pretty rough, especially at idle. I can feel a noticeable vibration, and sometimes it feels like it's struggling a bit when I accelerate from a stop.

The check engine light came on a few days ago, and I'm pretty sure it's related to a misfire. I haven't had a chance to get the codes pulled yet, but it definitely feels like one or more cylinders aren't firing correctly. This started happening somewhat suddenly.

Has anyone experienced anything similar with their VR30DDTT engine? I'm wondering if it could be spark plugs, ignition coils, or something more serious. Any advice on what to check first or common culprits for this model year and trim would be greatly appreciated before I take it to the shop. Thanks in advance!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 24, 2:47 PM

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ClearTheCode admin answer:

A rough idle and misfire in your 2018 Infiniti Q50 3.0t Red Sport are common symptoms that can point to several issues within the engine and drivetrain. The VR30DDTT engine, while powerful, can experience these problems.

Here's a breakdown of potential causes and steps:

  1. Check Engine Light & OBD Codes:

    • The first and most crucial step is to get the OBD-II codes read. A P0300 code indicates a random/multiple cylinder misfire, while P0301, P0302, etc., specify a misfire in a particular cylinder (e.g., Cylinder 1, Cylinder 2). These codes will narrow down your diagnostic path significantly.

  2. Common Causes for Misfires in VR30DDTT:

    • Spark Plugs: Worn or fouled spark plugs are a frequent cause of misfires. Given the performance nature of the Red Sport, spark plugs can degrade faster under aggressive driving conditions.
    • Ignition Coils: A failing ignition coil will prevent a spark plug from firing correctly, leading to a misfire in that specific cylinder.
    • Fuel Injectors: A clogged or faulty fuel injector can either deliver too much or too little fuel, disrupting combustion.
    • Vacuum Leaks: Leaks in the intake system can introduce unmetered air, causing the air/fuel mixture to be incorrect and leading to misfires, especially at idle.
    • Mass Air Flow (MAF) Sensor: A dirty or failing MAF sensor can send incorrect air intake readings to the ECU, leading to improper fuel delivery.
    • PCV Valve: A malfunctioning PCV valve can also contribute to vacuum issues or oil consumption, impacting engine performance.

  3. When to See a Shop:

    • If you've retrieved the OBD codes and they point to specific cylinder misfires, you can try replacing spark plugs and coils for the affected cylinder(s) as a DIY step if you're comfortable.
    • However, if the issue persists, or if the codes indicate more complex problems (e.g., P0420/P0430 for catalytic converter efficiency, P0171/P0174 for lean conditions), it's highly recommended to take your vehicle to a qualified Infiniti specialist. They have the advanced diagnostic tools and expertise to accurately pinpoint the root cause, which could involve checking fuel pressure, compression, or performing smoke tests for vacuum leaks. Continuing to drive with a persistent misfire can lead to catalytic converter damage and other costly repairs.
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