Injection System

All engines used in this section have a sequential Multi-Port Electronic Fuel Injection system. The MPI system is computer regulated and provides precise air/fuel ratios for all driving conditions. The Powertrain Control Module (PCM) operates fuel injection system.

The PCM regulates:

• Ignition Timing
• Air/Fuel Ratio
• Emission Control Devices
• Cooling Fan
• Charging System
• Idle Speed
• Vehicle Speed Control

Various sensors provide inputs necessary for PCM to correctly operate these systems. In addition to sensors, various switches also provide inputs to PCM. The PCM can adapt its programming to meet changing operating conditions.

Fuel is injected into intake port above intake valve in precise metered amounts through electrically operated injectors. The PCM fires injectors in a specific sequence. Under most operating conditions, PCM maintains an air fuel ratio of 14.7 parts air to 1 part fuel by constantly adjusting injector pulse width. Injector pulse width is length of time injector is open.

The PCM adjusts injector pulse width by opening and closing ground path to injector. Engine RPM (speed) and manifold absolute pressure (air density) are primary inputs that determine injector pulse width.