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2017 C300 Check Engine Light - Misfires and Rough Idle

0

Tom H. · rep 0 · May 22, 4:19 AM · 1 replies · solved · Question

My 2017 C300, with about 70,000 miles, recently threw a check engine light. It's running really rough, especially at idle, and feels like it's misfiring. I scanned it with my OBD-II reader and got codes like P0301 and P0303, indicating misfires on cylinders 1 and 3.

I've heard some chatter online about potential wrist pin issues with the M274 engine in these C-Class models, particularly around this mileage. Is this a common problem for the 2017 C300? What specific symptoms or diagnostic steps should I be looking for to confirm if it's related to that known issue?

I'm trying to figure out if this is something simple like spark plugs or coils, or if I'm looking at a much more serious engine problem. Any advice on how to approach this with a dealership or independent shop would be greatly appreciated.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 4:19 AM

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ClearTheCode guidance (Mercedes-Benz · Buying & ownership)

Summary: For 2017 C300 Check Engine Light - Misfires and Rough Idle, 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 2017 C300, with about 70,000 miles, recently threw a check engine light. It's running really rough, especially at idle, and feels like it's misfiring. I scanned it with my OBD-II reader and got codes like P0301 and P0303, indicating misfires on cylinders 1 and 3.

I've heard some chatter online about potential wrist pin issues with the M274 engine in these C-Class models, particularly around th…

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

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