Simple Checks (Do these first):
* Battery/Charging System: A weak battery or failing alternator can cause starting problems and erratic idling. Test the battery voltage (should be around 12.6V when not charging, higher when the engine's running) and the alternator's output voltage.
* Dirty or Corroded Battery Terminals: Clean the battery terminals and cable connections with a wire brush and baking soda solution. Corrosion restricts current flow.
* Fuel: Check the fuel level. A low fuel level can sometimes cause starting and idling issues, especially if the fuel pump is nearing the end of its life.
* Loose or Damaged Spark Plug Wires: Inspect the spark plug wires for cracks, damage, or loose connections. A bad connection can lead to misfires and poor running.
* Vacuum Leaks: Inspect all vacuum hoses for cracks, holes, or loose connections. A vacuum leak can drastically affect the idle and starting. Pay close attention to the hoses around the intake manifold.
More Involved Issues (Require more diagnosis):
* Crankshaft Position Sensor (CKP): This sensor tells the computer the position of the crankshaft. A faulty CKP will prevent the engine from starting or cause erratic running.
* Cam Position Sensor (CMP): Similar to the CKP, a faulty CMP will disrupt the engine timing, affecting starting and idling.
* Mass Airflow Sensor (MAF): A dirty or faulty MAF sensor provides inaccurate air flow readings to the computer, resulting in poor fuel mixture and rough running. Cleaning it (carefully, with MAF sensor cleaner) can sometimes help.
* Throttle Position Sensor (TPS): An incorrect TPS reading can cause poor idle and starting issues.
* Idle Air Control (IAC) Valve: This valve regulates air flow at idle. A dirty or faulty IAC valve can lead to low or erratic idle.
* Fuel Pump: A weak or failing fuel pump might not provide enough fuel pressure for starting or sustained idling. You might hear a weak whining sound from the fuel pump when you turn the key to the "on" position (but not cranking).
* PCV Valve: A clogged PCV valve can cause excessive crankcase pressure, affecting engine performance and potentially causing a rough idle.
* Ignition Coil(s): A failing ignition coil can cause misfires, leading to poor starting and running.
Troubleshooting Steps:
1. Start with the simple checks. These are the easiest and cheapest to address.
2. Use a code reader: A code reader (OBD-II scanner) can retrieve diagnostic trouble codes (DTCs) stored in the car's computer. These codes can point directly to the faulty component.
3. Check fuel pressure: A fuel pressure gauge is needed to check if the fuel pump is delivering adequate pressure.
4. Consult a repair manual: A repair manual specific to your 2001 Ford Mustang will provide detailed information on diagnosing and repairing these systems.
Important Note: If you're not comfortable working on your car yourself, it's best to take it to a qualified mechanic for diagnosis and repair. Attempting repairs without proper knowledge can potentially worsen the problem.
