Throttle Body Injector Assembly
The throttle body injector assembly consists of 2 castings: a throttle body and a fuel meter body. Throttle body casting incorporates an IAC valve to control air flow, and a throttle position sensor. Throttle body casting may contain ports to generate vacuum signals for EGR valve, MAP sensor and canister purge system.
The fuel meter body has a cover with built in pressure regulator, and fuel injector(s) to supply fuel to engine. The pressure regulator is a diaphragm-operated relief valve with injector pressure acting on one side and air cleaner pressure acting on the other.
The pressure regulator maintains a constant pressure drop of about 10 psi (.7 kg/cm2 ) across the injector, throughout all engine operating conditions. See Fig 1.
The fuel injector is a solenoid-operated device controlled by the ECM. The ECM activates the solenoid which lifts a normally closed ball valve off its seat. Fuel under pressure is injected in a conical spray pattern at the walls of throttle body bore, above the throttle valve. Excess fuel passes through the pressure regulator and is returned to the fuel tank.