Cylinder 3 Misfire Detected

What is P0303?

P0303 indicates the engine's computer has detected a misfire specifically in cylinder 3, which is a critical powertrain issue that can damage the catalytic converter if ignored. Based on real owner data, this code is most frequently triggered by ignition system failures, particularly in vehicles like the Ford F-150, Honda Accord, and Chevrolet Spark. Owners report it often occurs around 80,000-130,000 miles and can cause noticeable drivability problems.

Common Causes

• ●Faulty ignition coil on cylinder 3 (most frequently cited fix in owner reports)
• ●Worn or fouled spark plugs (commonly replaced alongside coils in maintenance)
• ●Potential head gasket issues mentioned specifically for Honda Accords by a service manager

Symptoms You May Notice

• ●Engine shudder or vibration, especially noted in Ford F-150 transmissions
• ●Check Engine Light is illuminated
• ●Reduced engine power and rough idling
• ●Occasional traction loss or fishtailing in performance vehicles like the Ford Mustang

How to Fix It

• ●Replace the faulty ignition coil, often recommended to replace all coils simultaneously ($280 for parts DIY, up to $400+ at a shop, moderate difficulty)
• ●Replace spark plugs, frequently done with coil service (cost included in coil job, easy to moderate difficulty)
• ●Complete transmission fluid flush for specific shudder issues under technical service bulletins, as reported for some Ford F-150s (potentially covered under warranty, otherwise $500+)