Hey everyone, I'm hoping someone can help me out. My 2017 Mercedes-Benz C300 (W205) has been running really rough lately, especially at idle. The check engine light came on yesterday, and when I scanned it, I got a P0302 code, indicating a misfire on cylinder 2. The car feels a bit sluggish under acceleration too. I've heard these M274 engines can have injector issues or carbon buildup. Any ideas on what I should check first before taking it to the dealer? I'm trying to avoid a huge repair bill if it's something simple.
2017 C300 Rough Idle and CEL - P0302 Code
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Brian F. · rep 0 · May 22, 4:12 AM · 1 replies · solved · Question
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ClearTheCode Admin
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ClearTheCode guidance (Mercedes-Benz · Diagnostics & codes)
Summary: For 2017 C300 Rough Idle and CEL - P0302 Code, work through these steps on your 2016+ vehicle:
- Confirm the symptom — note when it happens (cold start, highway, after fuel fill, etc.).
- Scan codes — save all pending/stored DTCs; don't clear until you've recorded them.
- Check TSBs & recalls — look up your VIN for open campaigns and known fixes.
- Inspect the obvious — related fuses, connectors, fluid level, and recent repairs.
- Test the common fix — follow model-specific service procedures; one change at a time.
- Escalate if needed — burning smell, no brakes, overheating, or stalling in traffic → shop visit.
Owner reported: Hey everyone, I'm hoping someone can help me out. My 2017 Mercedes-Benz C300 (W205) has been running really rough lately, especially at idle. The check engine light came on yesterday, and when I scanned it, I got a P0302 code, indicating a misfire on cylinder 2. The car feels a bit sluggish under acceleration too. I've heard these M274 engines can have injector issues or carbon buildup. Any ideas …
This is educational guidance, not a substitute for hands-on diagnosis.