Throttle Position (TP) Sensor

The throttle position sensor is mounted on the side of the plenum chamber inlet neck and is directly coupled to the throttle butterfly shaft. The throttle position sensor is a resistive device supplied with a voltage from the ECM. Movement of the accelerator pedal causes the throttle valve to open, thus rotating the wiper arm within the throttle position sensor which in turn varies the resistance in proportion to the valve position. The ECM lengthens the injector open time when it detects a change in output voltage (rising) from the throttle position sensor.

In addition, the ECM will weaken the mixture when it detects the throttle position sensor output voltage is decreasing under deceleration and will shorten the length of time the injectors are open. When the throttle is fully open, the ECM will detect the corresponding throttle position sensor voltage and will apply full load enrichment. This is a fixed percentage and is independent of temperature. Full load enrichment is also achieved by adjusting the length of the injector open time. When the throttle is closed, overrun fuel cut off or idle speed control may be facilitated dependent on other inputs to the ECM.

A further improvement in 1989 is the fitting of a "self adaptive" throttle potentiometer. This means that adjustment of throttle potentiometer is no longer possible. It also means that potentiometer setting is not lost, for example, when throttle stop wear occurs.