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2018 Challenger R/T Misfire on Cylinder 3 - P0303

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Amanda S. · rep 0 · May 22, 5:39 AM · 1 replies · solved · Question

My 2018 Dodge Challenger R/T, 5.7L Hemi, started running rough last week. The check engine light came on, and when I scanned it, I got a P0303 code. It feels like a definite misfire, especially noticeable at idle and under light acceleration.

I've checked the spark plug on cylinder 3, and it looked okay, but I haven't replaced it yet. The car has about 75,000 miles on it.

Could this be a bad coil pack, an injector, or something more serious? Any common issues with these engines causing P0303?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 5:39 AM

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ClearTheCode guidance (Dodge · Diagnostics & codes)

Summary: For 2018 Challenger R/T Misfire on Cylinder 3 - P0303, 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: My 2018 Dodge Challenger R/T, 5.7L Hemi, started running rough last week. The check engine light came on, and when I scanned it, I got a P0303 code. It feels like a definite misfire, especially noticeable at idle and under light acceleration.

I've checked the spark plug on cylinder 3, and it looked okay, but I haven't replaced it yet. The car has about 75,000 miles on it.

Could this be a bad coi…

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

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