2002 Ford F150 4.6L 'W' V8 P0303 and P0316 Fault Code Diagnosis at 130,000 Miles
Hi, I recently purchased a 2002 Ford F15-0 XLT with the 4.6L 'W' engine (V8). It ran smoothly for approximately 2,000 miles before suddenly becoming rough and triggering the 'Service Engine Soon' light. Diagnostic trouble codes P0303 and P0316 have been detected. The truck has now reached 130,000 miles. The previous owner provided complete service records, including a tune-up with spark plugs replaced at 90,000 miles. This is a standard 2WD model equipped with the 4R70W transmission and features the factory tow package with a 3:55 limited-slip rear axle. Fuel efficiency has consistently been around 16 MPG in combined city/highway driving—similar to what earlier 1992 F150 models achieved when this truck was originally built. Given its history of careful maintenance, I'm seeking guidance on how to properly diagnose and resolve these issues. Any insights or recommended troubleshooting steps would be greatly appreciated.
P0303 typically indicates a misfire in cylinder 3, which is often caused by one or more faulty ignition coils. P0316 suggests a poor engine idle or startup condition, possibly due to worn spark plugs, weak fuel delivery, or issues with the mass airflow sensor. Given the age and mileage of this vehicle, inspecting the ignition coils and ensuring proper spark plug condition is a high-priority step in diagnosis.