Exam 30: Electronic Fuel Injection

While discussing PFI systems, Technician A says the PCM provides the proper air/fuel ratio by controlling the fuel pressure. Technician B says the PCM provides the proper air/fuel ratio by controlling the injector pulse width. Who is correct?

Fuel injectors are electromechanical devices.

Name three advantages of a throttle-by-wire [ETC] system.

Idle speed control is a function of the PCM.

MAP output is the same as what is measured on a vacuum gauge. When intake vacuum is high, MAP voltage is high.

Technician A says an air/fuel ratio sensor responds to minor changes in the air/fuel mixture. Technician B says that when an air/fuel ratio sensor is used on an OBD-II vehicle, both the upstream and downstream sensors must be air/fuel ratio type sensors. Who is correct?

A mass airflow-type fuel injection system uses a ____________________ sensor to determine the amount of air entering the engine.

Technician A says the vacuum hose on the fuel pressure regulator of a PFI system is connected to the intake manifold. Technician B says the fuel pressure regulator of a TBI injection system doesn't need a vacuum hose to regulate pressure because the injectors are located above the throttle plate where the air pressure is constant. Who is correct?

Explain the basic operation of a CPI system.

CPI (central multiport injection)injectors are located in the lower half of the intake manifold.

____________________ systems inject gasoline directly into the cylinders.

An O-ring at the base of a fuel injector ______.

Fuel trim is being discussed. Technician A says a positive fuel-trim value means the PCM detects a lean mixture and is increasing the pulse width to add more fuel to the mixture. Technician B says LTFT [long-term fuel trim] is erased when the ignition is turned off. Who is correct?

During closed loop engine mode, injector pulse width is controlled according to predetermined parameters held in the PCM's memory.

The PCM may order a richer fuel mixture when the engine is overheating.

Describe the purpose of an ECT signal on an EFI system.

The ideal, or stoichiometric mixture of air and fuel for a gasoline engine is ____________________ to 1.

Identify the some of the advantages of gasoline direct injection (GDI)systems.

The injectors on a modern port fuel injection system receive fuel from the ____________________.

The strength of the mass airflow (MAF)signal is determined by the energy needed to keep the heated sensing element at a constant temperature above the incoming ambient air temperature.