- Faulty Throttle Position Sensor (TPS): The TPS is responsible for providing the engine control unit (ECU) with information about the position of the throttle valve. If the TPS is faulty or damaged, it may send incorrect signals to the ECU, causing the engine to start only when the accelerator pedal is pressed all the way down.
- Faulty Idle Air Control (IAC) Valve: The IAC valve controls the amount of air that bypasses the throttle valve when the engine is idling. If the IAC valve is faulty or clogged, it can prevent the engine from idling properly, causing it to stall or run rough. To start the engine, you may need to press the accelerator pedal all the way down to provide enough air for the engine to run.
- Vacuum Leaks: Vacuum leaks can cause the engine to run lean, which can lead to difficulties starting and stalling. Check for any loose or disconnected vacuum hoses, particularly around the intake manifold and throttle body.
- Fuel System Issues: Check the fuel pressure to ensure that the fuel system is delivering enough fuel to the engine. A weak fuel pump, clogged fuel filter, or faulty fuel injector can cause the engine to start with difficulty.
