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 Control (Fuel Injected Models)
All electronic fuel injected (EFI) models are equipped with an electrically-pulsed injector located in a throttle body unit on the intake manifold. The ECM, responding to inputs from data sensors, constantly adjusts air/fuel mixture to maintain engine performance. The ECM controls the pulse width (injector "on" time) to provide the proper amount of fuel for the specific engine requirement. Increasing the injector pulse width, richens the air/fuel ratio. Decreasing the injector pulse width, leans the air/fuel ratio.
When ECM responds to signals received from oxygen sensor to adjust fuel mixture, the CCC system is in closed loop operation. Under certain operating conditions, the ECM may ignore inputs from the oxygen sensor and use a pre-programmed calibration program to control the engine under that particular operating mode. Operating conditions which cause the ECM to ignore oxygen sensor signals cause the CCC system to operate in open loop mode.
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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.