2007 Mustang GT 4.6L Running Rough with P0316 and P1000 Fault Codes
I own a 2007 Ford Mustang GT with a 4.6L engine. My OBD2 scanner is showing both P0316 (Crankshaft Position Sensor Circuit Malfunction) and P1000 (Fuel System Pressure Too Low) fault codes. I recently replaced all eight spark plugs and coil packs, but the vehicle's performance has actually worsened compared to before. The car now runs roughly, with poor acceleration and increased idle fluctuations. I'm concerned that the repair may have caused further issues or that I missed a critical step in diagnosing the root cause.
Did you install the correct type of spark plugs? Aftermarket, low-quality plugs can lead to misfires and worsen engine performance. Were all eight coil packs replaced? If not, this could contribute to inconsistent ignition. Is your vehicle running stock (no modifications)? Start with cleaning the Mass Airflow Sensor (MAF) — avoid using an oiled air filter as it can interfere with airflow readings. Check that all coil connectors are securely tightened and inspect for bent or damaged pins. Ensure your scanner is capable of displaying live data, such as engine RPM, fuel trim, and misfire counts. Consider checking fuel pressure under KOEO (Key On, Engine Off) conditions — observe if the pressure drops more than X psi within 5 minutes. This test can be tricky on a 4.6L V8 due to its design. What did your old spark plugs look like? Were they wet, dry, black, or tan? This information helps assess combustion efficiency.