P0301 Code: Cylinder 1 Misfire Detected
The engine computer has detected misfires specifically in cylinder 1 — that cylinder is not firing cleanly while the others are.
What this means for driving
A single-cylinder misfire still deserves prompt attention, because unburned fuel from that cylinder can overheat and damage the catalytic converter. If the check-engine light is flashing, the engine is shaking badly, or power has dropped sharply, stop driving and arrange a tow rather than continuing.
When in doubt, have a mechanic assess it promptly. If any of the red-flag symptoms below are present, stop driving and arrange a tow rather than risking it.
Important: This page is general information only — not professional mechanical advice and not a diagnosis for your specific vehicle. Fault causes and severity vary by make, model, year, and condition. A qualified mechanic should confirm any diagnosis before you make driving decisions or authorize repairs.
Red-flag symptoms: stop and get help
- Check-engine light flashing
- Severe shaking or major loss of power
- Strong fuel smell from the exhaust
- Engine stalling repeatedly
Symptoms of P0301
- Rough idle or vibration
- Hesitation on acceleration
- Loss of power
- Poor fuel economy
- Check-engine light on or flashing
Most likely causes, ranked
- Worn or fouled spark plug in cylinder 1
- Failing ignition coil on cylinder 1
- Clogged or faulty fuel injector for cylinder 1
- Vacuum leak near cylinder 1's intake runner
- Low compression in cylinder 1 (worn rings, valves, or head gasket)
How a mechanic diagnoses it
- Plug and coil for cylinder 1 inspected; a coil swap to another cylinder shows whether the misfire follows the coil.
- Injector tested for proper spray and electrical operation.
- Compression test on cylinder 1 if ignition and fuel check out.
Likely fixes
- Replace spark plug(s) (DIY)
- Replace ignition coil (cylinder 1)
- Replace fuel injector (cylinder 1)
- Repair vacuum leak
Repair costs vary by vehicle, region and shop. Get a quote from a local mechanic.
Related codes
- P0300: Random/Multiple Cylinder Misfire Detected
- P0302: Cylinder 2 Misfire Detected
- P0303: Cylinder 3 Misfire Detected
- P0171: System Too Lean (Bank 1)
CheckMyCarCode content is general information only and is not a substitute for professional diagnosis. Trouble-code meanings are standardized for generic (P0xxx) codes, but causes, severity, and repairs vary by vehicle. If your car shows a red-flag symptom, stop driving and get professional help.