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2018 RX 350 Rough Idle and Check Engine Light - P0302

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Brian F. · rep 0 · May 22, 4:40 AM · 1 replies · solved · Question

Vehicle: 2018 Lexus RX 350 F Sport

Hey everyone,

I've got a 2018 Lexus RX 350 F Sport with about 75,000 miles on it. Recently, I've noticed a really rough idle, especially when I'm stopped at a light or in traffic. The whole car shudders a bit, and it feels like it's struggling.

Yesterday, the check engine light came on. I took it to AutoZone for a quick scan, and it pulled a P0302 code, indicating a misfire on cylinder 2. Has anyone experienced this with their RX 350? What was the fix? I'm hoping it's not something major.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 4:40 AM

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ClearTheCode admin answer:

A P0302 code indicates a misfire detected in cylinder 2. This is a common issue with several potential causes. Addressing it promptly is important to prevent further engine damage.

Common Causes:

  1. Faulty Spark Plug: A worn, fouled, or damaged spark plug in cylinder 2 is a very common culprit.
  2. Defective Ignition Coil: The ignition coil for cylinder 2 might be failing, preventing a strong spark.
  3. Clogged or Faulty Fuel Injector: If the fuel injector for cylinder 2 isn't delivering fuel correctly, it can cause a misfire.
  4. Vacuum Leak: A vacuum leak near cylinder 2 could lean out the air/fuel mixture, leading to misfires.
  5. Low Compression: Less common, but internal engine issues like worn piston rings or valve problems can cause low compression and misfires.

Troubleshooting Steps:

  1. Confirm the Code: If you haven't already, get a professional diagnostic scan to confirm P0302 and check for any other pending codes.
  2. Visual Inspection: Check the spark plug and ignition coil for cylinder 2. Look for any signs of damage, oil fouling, or corrosion. You can sometimes swap the coil with an adjacent cylinder to see if the misfire moves (e.g., P0302 becomes P0304).
  3. Fuel System Check: A mechanic can test fuel pressure and injector function to ensure proper fuel delivery.
  4. Compression Test: If other checks don't yield results, a compression test will determine if there's an internal engine issue.

When to See a Shop:

  • Immediately: If the check engine light is flashing, this indicates a severe misfire that could damage the catalytic converter. Stop driving and have it towed.
  • Soon: If the rough idle persists and the check engine light is solid, it's best to have a qualified Lexus technician diagnose and repair the issue. They have specialized tools to pinpoint the exact cause efficiently.
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