Throttle Position Sensor: Description and Operation

Throttle Potentiometer
To ensure the vehicle road performance is satisfactory, with good throttle response, acceleration enrichment is necessary. Signals are provided by the throttle potentiometer, which is mounted on the throttle spindle and indicates the throttle position to the ECU. When the throttle is opened the fuelling is enriched and when closed the fuelling is weakened. When the throttle is opened very quickly, all the injectors are simultaneously energized for one pulse.

This ensures that there is enough fuel available at the inlet ports for the air admitted by the sudden opening of the throttle. The duration of this extra pulse is controlled by the engine temperature signal, and is longer with a cold engine.

Lengthening the normal injection pulses is done in proportion to the rate at which the throttle is opened and it takes a short time to decay when the throttle movement stops. Enrichment in this way is also varied according to the engine temperature. The fuel cutoff function is controlled by the throttle potentiometer, and the conditions under which it occurs are programmed into the ECU memory.