1. Control engine power and speed

• The throttle valve regulates airflow into the engine
• More air allows more fuel to burn → more power
• Less air reduces power (idle or cruising)

2. Respond to driver input

• It opens when you press the accelerator and closes when you release it
• This is how your car speeds up or slows down

3. Maintain stable idling

• Keeps a small, controlled airflow when the engine is idling
• Prevents stalling

4. Improve fuel efficiency

• Ensures the correct air-to-fuel ratio for efficient combustion

5. Support emissions systems

• Helps systems like Exhaust Gas Recirculation (EGR) work properly
• Reduces harmful exhaust emissions

6. Smooth engine operation (especially in modern cars)

• In electronic systems, it works with sensors and the ECU to optimize performance and drivability

1. Rough or unstable idle

• Engine shakes or RPM goes up and down at idle
• May feel like it’s about to stall

2. Poor acceleration

• Delayed response when pressing the gas pedal
• Sluggish or weak power

3. Engine stalling

• Engine may shut off when stopping or idling
• Especially noticeable at traffic lights

4. Check engine light

• Fault codes related to throttle position or airflow
• Common in electronic (drive-by-wire) systems

5. Jerking or hesitation

• Sudden surges or jerks while driving
• Inconsistent throttle response

6. Reduced power (limp mode)

• Vehicle may limit speed and power to protect the engine

7. High or low idle speed

• Engine revs too high or struggles to stay running

8. Poor fuel economy

• Incorrect air-to-fuel ratio leads to higher fuel consumption