A throttle position sensor (TPS) is a sensor used to monitor the position of the throttle in an internal combustion engine. The sensor is usually located on the butterfly spindle so that it can directly monitor the position of the throttle valve butterfly.
The sensor is usually a potentiometer, and therefore provides a variable resistance dependent upon the position of the valve (and hence throttle position).
The sensor signal is used by the engine control unit (ECU) as an input to its control system. The ignition timing and fuel injection timing (and potentially other parameters) are altered depending upon the position of the throttle, and also depending on the rate of change of that position. For example, in fuel injected engines, in order to avoid stalling, extra fuel may be injected if the throttle is opened rapidly (mimicking the accelerator pump of carburetor systems).
More advanced forms of the sensor are also used, for example an extra closed throttle position sensor (CTPS) may be employed to indicate that the throttle is completely closed.
Some ECUs also control the throttle position and if that is done the position sensor is utilised in a feedback loop to enable that control.
Related to the TPS are accelerator pedal sensors, which often include a wide open throttle (WOT) sensor. The accelerator pedal sensors are used in "drive by wire" systems, and the most common use of a wide open throttle sensor is for the kickdown function on automatic transmissions.
It senses Manifold Absolute Pressure (MAP). The vehicle computer calculates how much fuel to deliver to the engine based on the amount of load being applied to the engine. The computer uses manifold pressure, barometric pressure, engine RPM and throttle angle to determine engine load. Fuel ratio and spark timing are then fine tuned by the computer using additional sensors, this also helps to control fuel economy and emissions. Some vehicles use a Mass Air Flow sensor to measure the amount of air entering the engine, this also is used to determine engine load, in some cases there may be a MAP sensor and a MAF sensor. In that configuration the MAP is used for Barometric pressure and is a back up should the MAF fail, the computer will illuminate the Service Engine Soon lamp and use a calculated air fuel mixture to allow the driver to get to a repair shop without damaging the catalytic converter.
The MAP sensor doubles as a barometric sensor. The computer will read barometric pressure when the key is turned on prior to engine cranking and then every time the computer senses wide open throttle it will check Baro pressure again.
Nspect and test the crankcase ventilation system, When was the last tune-up-Having the wrong PCV valve can dilute and lean out the A/F mix-
Sunday, December 6th, 2009 AT 4:12 PM