Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Fuel Injection System - 2.8L/3.1L PFI: Description: Notes
The Port Fuel Injection (PFI) system is controlled by the Electronic Control Module (ECM). The ECM monitors engine operation and environmental conditions. In addition to other functions, ECM output signals provide correctional adjustments for air/fuel mixture and idle speed.
Standard PFI systems feature simultaneous double-fire injection. Fuel injectors are pulsed once for each engine revolution, each spray providing 1/2 the fuel required for the combustion process.
In all systems, constant fuel pressure is maintained to the injectors. Air/fuel mixture is regulated by the time that injector stays open (pulse width). Various sensors provide information to the ECM to control pulse width. There are 2 major PFI sub-systems; fuel delivery system and electronic control system.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.