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2018 RX 350 Rough Idle and Misfire Codes

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Jennifer H. · rep 0 · May 22, 4:42 AM · 1 replies · solved · Question

Hey everyone, I'm having some trouble with my 2018 Lexus RX 350 F Sport. Lately, it's developed a really rough idle, especially when I'm stopped at a light. The engine feels like it's shaking more than usual.

A few days ago, the Check Engine Light came on. I had it scanned, and it's showing P0301 (Cylinder 1 Misfire Detected) and P0300 (Random/Multiple Cylinder Misfire Detected).

I'm wondering if this is a common issue with these models. Could it be spark plugs, or something more serious? Any advice on what to check first before taking it to the dealer?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 4:42 AM

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ClearTheCode guidance (Lexus · Engine & drivetrain)

Summary: For 2018 RX 350 Rough Idle and Misfire 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 some trouble with my 2018 Lexus RX 350 F Sport. Lately, it's developed a really rough idle, especially when I'm stopped at a light. The engine feels like it's shaking more than usual.

A few days ago, the Check Engine Light came on. I had it scanned, and it's showing P0301 (Cylinder 1 Misfire Detected) and P0300 (Random/Multiple Cylinder Misfire Detected).

I'm wondering i…

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

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