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2018 Q50 Red Sport - Rough Idle and Flashing CEL Under Acceleration

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Melissa G. · rep 0 · May 22, 5:04 AM · 1 replies · solved · Question

Vehicle: 2018 Infiniti Q50 Red Sport 400

Hey everyone, I'm having some trouble with my 2018 Infiniti Q50 Red Sport 400 and hoping someone here has experienced something similar. Lately, it's developed a really rough idle, almost like it's struggling to stay smooth, especially when I'm stopped at a light.

The bigger concern is that sometimes when I accelerate, particularly from a stop or at lower speeds, the car hesitates significantly, and the Check Engine Light starts flashing. It doesn't always stay on, but the flashing is definitely alarming. It feels like it's losing power for a second or two.

I've checked the basic things like the air filter, and it looks fine. I'm wondering if this could be spark plugs, ignition coils, or something more serious with the turbos. Any ideas on what I should look into first before taking it to the dealer?

✓ Accepted solution

ClearTheCode Admin

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

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ClearTheCode admin answer:

A rough idle, hesitation under acceleration, and a flashing Check Engine Light (CEL) on your 2018 Infiniti Q50 Red Sport 400 strongly suggest an engine misfire. A flashing CEL indicates a severe misfire that could potentially damage the catalytic converter due to unburnt fuel entering the exhaust.

Here's a breakdown of common causes and steps:

  1. Retrieve OBD-II Codes: The absolute first step is to get the diagnostic trouble codes (DTCs) from your vehicle's OBD-II port. A flashing CEL almost guarantees stored misfire codes (P0300 for random misfire, or P0301-P0306 for specific cylinder misfires). Many auto parts stores offer free code reading services.
  2. Common Misfire Causes:
    • Spark Plugs: Worn or fouled spark plugs are a very common cause of misfires. Given the age and performance nature of your Q50 Red Sport, they might be due for replacement, especially if you're past the recommended service interval.
    • Ignition Coils: A failing ignition coil on one or more cylinders will prevent proper spark, leading to a misfire. If you have a specific cylinder misfire code (e.g., P0303), you can try swapping the coil with a known good cylinder to see if the misfire moves.
    • Fuel Injectors: Clogged or faulty fuel injectors can cause an improper fuel-air mixture, leading to misfires. This is less common than spark plugs or coils but still a possibility.
    • Vacuum Leaks: Unmetered air entering the engine can disrupt the fuel-air ratio, causing a rough idle and misfires.
    • Low Compression: While less likely on a relatively newer engine, low compression in a cylinder due to internal engine wear could cause a persistent misfire.
  3. When to See a Shop:
    • Immediately if CEL is Flashing: A flashing CEL means stop driving if possible, or drive very gently to the nearest safe location or repair shop. Continued driving with a severe misfire can lead to expensive catalytic converter damage.
    • If Codes Point to Specific Cylinders: If you get P030x codes, a qualified technician can perform further diagnostics, such as spark plug inspection, coil testing, and potentially fuel pressure/injector tests.
    • If DIY Diagnostics Don't Resolve: If replacing spark plugs or coils (if you're comfortable doing so) doesn't fix the issue, or if the codes are more complex than simple misfires, it's best to have a professional diagnose the problem. They have specialized tools to test fuel pressure, vacuum, and perform more in-depth engine diagnostics.

Do not ignore a flashing CEL. Address this issue promptly to prevent further damage.

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