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2017 C300 Engine Misfire & Rough Idle - Check Engine Light!

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Mike T. · rep 0 · May 22, 4:21 AM · 1 replies · solved · Question

My 2017 Mercedes-Benz C300 (W205) with the M274 engine has been acting up lately. I've noticed a really rough idle, especially when cold, and the engine feels like it's misfiring under acceleration. The check engine light came on a few days ago and hasn't gone off.

I took it to a local shop, and they pulled codes P0302 and P0304, indicating misfires on cylinders 2 and 4. They suggested it could be anything from spark plugs to injectors, but I've heard about some wrist pin issues with these engines. Is this a common problem for the 2017 C300? What should I be looking for?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 4:21 AM

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ClearTheCode guidance (Mercedes-Benz · Buying & ownership)

Summary: For 2017 C300 Engine Misfire & Rough Idle - Check Engine Light!, 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 Mercedes-Benz C300 (W205) with the M274 engine has been acting up lately. I've noticed a really rough idle, especially when cold, and the engine feels like it's misfiring under acceleration. The check engine light came on a few days ago and hasn't gone off.

I took it to a local shop, and they pulled codes P0302 and P0304, indicating misfires on cylinders 2 and 4. They suggested it could b…

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

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