The Air/Fuel System

1. Throttle Link. It connects to your gas pedal. The screw just to the right adjusts your Base idle (the computer adjusts it based on this setting.)

2. Choke/Idle control motor. The entire bottom portion is where the coolant runs into to warm up your intake in the morning and the Idle Speed control (ISC) motor is mounted. The ISC adjusts how much air gets let past the butterfly valve at idle. This helps to maintain a reasonable idle. This is a stepper motor that constantly adjusts how much air makes it through the Throttle Body by opening and closing an air-bypass valve. These motors have been known to fail.

3. Butterfly Valve. Adjusts how much air is allowed into the Intake Manifold. This is the most restrictive part of the intake.

4. Basic Idle Setpoint Screw (BISS). Make sure you have a rubber plug here. Otherwise you will develop a vacuum leak.

5. Throttle Position Sensor (TPS). Just as it implies, it senses the position of the gas pedal and sends adjusted information to the Idle Speed control (ISC). The ISC uses this reading for maintaining your idle.

6. Fuel Return Line. This is where the extra fuel returns to the fuel take after being heated up in the engine bay.

7. Fuel Rail. This is the aluminum tube that allows the fuel to absorb heat from the engine. It also supplies the Fuel Injectors with fuel. At the very end is the Fuel Pressure Regulator. It maintains a specific pressure inside the fuel rail and sends any extra pressure (fuel) back to the tank.

8. Fuel Injectors. They take the pressurized fuel and mist it into the intake (right in front of the intake valves. This is where the air and fuel get sucked into the cylinders.)

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