1. Fuel Pressure Regulator: A faulty fuel pressure regulator can cause the fuel pressure to drop after the engine is turned off, making it hard to start. Have the fuel pressure checked and replace the regulator if necessary.
2. Fuel Pump: A weak or failing fuel pump can also cause low fuel pressure, especially when the engine is hot. Check the fuel pressure and replace the pump if necessary.
3. Coolant Temperature Sensor: A faulty coolant temperature sensor can send incorrect signals to the engine control unit (ECU), causing it to over-fuel the engine when it's hot. This can lead to hard starting and rough idle. Test the coolant temperature sensor and replace it if necessary.
4. Idle Air Control Valve (IACV): A dirty or faulty IACV can cause the engine to stall or run rough at idle. Clean the IACV and check for proper operation. Replace the IACV if necessary.
5. Vacuum Leaks: Vacuum leaks can cause the engine to run lean, which can lead to hard starting and stalling. Check for any vacuum leaks and repair them as necessary.
6. Battery: A weak or failing battery can also cause hard starting, especially when the engine is hot. Have the battery tested and replace it if necessary.
