Your 2021 Mercedes-Benz C-Class has developed a telltale stumble, and the scan reveals P0301—Cylinder 1 Misfire Detected. Unlike random misfire codes, this specific fault gives you a clear starting point for investigation. But why cylinder 1 specifically, and what makes the M264 engine unique in this regard?
Understanding Cylinder 1 Position
In Mercedes' inline-four M264 engine, cylinder 1 is positioned at the front of the engine, closest to the accessory drive. This location exposes it to slightly different thermal conditions and accessory belt vibrations compared to other cylinders. While not dramatically different, subtle variations in operating conditions can cause single-cylinder problems.
Primary Suspects for Cylinder 1 Misfires
When investigating a cylinder-specific misfire, start with components unique to that cylinder:
- Ignition coil failure - The coil-on-plug design means each cylinder has its own coil, and they fail independently
- Spark plug fouling or damage - Carbon buildup, oil contamination, or electrode wear specific to that cylinder
- Fuel injector malfunction - Direct injectors can develop deposits or electrical failures
- Compression loss - Valve sealing issues or cylinder wall problems
- Injector wiring issues - Connector problems or chafed wires to cylinder 1 specifically
The Coil Swap Test
This simple diagnostic technique can quickly identify ignition-related problems:
- Note the current code (P0301 - Cylinder 1)
- Swap the ignition coil from cylinder 1 with cylinder 3
- Clear the fault codes
- Drive until the check engine light returns
- Read codes again—if the misfire followed the coil (now P0303), the coil is faulty
This same test works for spark plugs. If the misfire stays at cylinder 1 despite swapping components, the issue is with the fuel delivery system or compression.
Direct Injection Challenges
The M264 engine uses high-pressure direct injection, spraying fuel directly into the combustion chamber. These injectors operate at thousands of PSI and can develop carbon deposits on the tips that affect spray patterns. Mercedes recommends periodic injector cleaning or fuel system treatments to maintain proper operation.
Repair Costs for 2021 C-Class Misfire
- Single ignition coil replacement: $150-$280
- Spark plug replacement (recommended all four): $220-$380
- Fuel injector replacement (single): $400-$700
- Fuel injector cleaning service: $150-$250
- Compression test diagnostic: $100-$200