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2018 Q50 3.0t Misfire and Rough Idle - P030x Codes

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Heather Y. · rep 0 · May 22, 5:04 AM · 1 replies · solved · Question

Hey everyone, I'm having a really frustrating issue with my 2018 Infiniti Q50 Red Sport 400. Lately, it's developed a rough idle, especially when cold, and I've noticed a significant drop in power. The check engine light came on, and when I scanned it, I got multiple misfire codes like P0301, P0303, and P0305.

I've tried replacing the spark plugs, but the problem persists. It feels like the engine is struggling, and sometimes it even stumbles under acceleration. The car has about 70,000 miles on it.

Has anyone else experienced this with their VR30DDTT engine? What was the fix? I'm hoping it's not something major like a turbo issue.

✓ Accepted solution

ClearTheCode Admin

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

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ClearTheCode guidance (Infiniti · Engine & drivetrain)

Summary: For 2018 Q50 3.0t Misfire and Rough Idle - P030x Codes, work through these steps on your 2016+ vehicle:

  1. Confirm the symptom — note when it happens (cold start, highway, after fuel fill, etc.).
  2. Scan codes — save all pending/stored DTCs; don't clear until you've recorded them.
  3. Check TSBs & recalls — look up your VIN for open campaigns and known fixes.
  4. Inspect the obvious — related fuses, connectors, fluid level, and recent repairs.
  5. Test the common fix — follow model-specific service procedures; one change at a time.
  6. Escalate if needed — burning smell, no brakes, overheating, or stalling in traffic → shop visit.

Owner reported: Hey everyone, I'm having a really frustrating issue with my 2018 Infiniti Q50 Red Sport 400. Lately, it's developed a rough idle, especially when cold, and I've noticed a significant drop in power. The check engine light came on, and when I scanned it, I got multiple misfire codes like P0301, P0303, and P0305.

I've tried replacing the spark plugs, but the problem persists. It feels like the engin…

This is educational guidance, not a substitute for hands-on diagnosis.

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