Throttle Position Sensor
Throttle Position Sensor (potentiometer)
Potentiometer type sensors are composed of variable resistors that have a slide contact,
which changes its position as the throttle butterfly moves.
A voltage is supplied to the sensor by the E.C.U. As the throttle position changes, the
output voltage from the sensor changes, this in turn is recognised and a comparison made
by the E.C.U to its memory. These sensors are adjusted by loosening the sensor mounting
screws. (It is critical that you follow the manufacturer’s set-up procedure)
For example:
The idle position is recognised by the lowest voltage reading through the sensor but in
contrast, the maximum power signal is recognised by the highest reading at the full throttle
position of the sensor travel. It is important that both signals are correct.
Checking the Throttle Position Sensor
What type of TPS is this?
The one we were using was the Switch type Throttle position sensor
Explain its internal operation and why your voltage changes.
A throttle position sensor provides very important information to the engines computer.
The computer uses that data to give the driver more or less engine power when needed and very often drivers can experience bad or faulty TPS when engine is running rough or not giving enough power.
The internal operation of the TPS switch is there are three contacts, the middle one is moved by groves that moves between the two outer contacts, the middle contact always stay on idle pin when throttle is less than 1.5' open . this will send voltage to the ECU so that it knows its on idle . When the throttle is open less than 70' no voltage is sent.When the throttle is opened more than 70' the middle contact comes into contact with the power switch contact sending another voltage to the ECU to let it know the engine needs more fuel.
NOTE: Always use a 5V supply
Throttle Position Angle
Things that can happen if yous throttle position is in bad condition:
Bucking or and jerking of the car
Idle surging of the car
Sudden stalling of the car engine when driving
Hesitation while the driver of the car is trying to accelerate.
Sudden surge in car's speed while driving on the highway.
So what happens when the throttle position sensor bad or faulty.well the computer will be getting the wrong information the engine malfunction indicator light will be on driver will also be experiencing difficulty when changing gears. The fuel economy of the car drops drastically.
I also got 2 short clips that we recorded while were testing the TPS .
Throttle Position Switch
There is an idle position signal that is used mainly for fuel cut-off control and ignition timing
corrections. The power signal is created at full throttle and is used for increasing fuel
injection volume which in turn increases engine power output. Note there is no switching at
part throttle.
Throttle position switch detects throttle position at idle or full throttle by using switch
contacts that are connected or disconnected as throttle position changes.
This type of switch can have two or three contact positions and is usually checked and
adjusted using a multi-meter.
Adjustment is made by loosening the mounting screws and rotating the switch assembly.
On - Off type throttle position switches can have:
Two position (three pin) or
Three position (four pin).
Note: PSW means power switch (WOT)
IDL means idle circuit
E means earth
Plot your findings on the graph
Throttle Valve Opening.
When it is idling the ECU knows the throttle is closed with certain resistance when acceleration pedal is fully pushed the ECU knows the throttle is open with certain resistance.
Manifold Absolute Pressure (MAP)
Wire up a map (manifold absolute pressure) sensor with a 5 V feed and earth. Measure
the return voltage from the third wire.
Using a mity-vac apply vacuum to the map sensor. Plot the voltage return in relation to the
vacuum applied.
Vacuum:
Explain the internal operation of this sensor and why the output voltage changes
The sensor consists of a piezoresistive silicon chip an integrated circuit (IC) A perfect vacuum is applied to the other side when pressure in te intake manifold changes the silicon ship flex's causing changes in its resistance . The varying resistance of the sensor causes a change in signal voltage at the PIM ( pressure intake manifold) terminal.
The Map sensor - Manifold absolute pressure sensor is used by the Engine control unit to measure the air intake vacuum and pressure. The Map sensor sends a signal voltage back to the Engine control unit which it uses to help calculate the fueling and ignition for the engine. The Fueling is altered my means of the injection duration and the ignition is either advanced or retarded.
The manifold absolute pressure contains diaphragm and a piezo-electric circuit which converts the measurement into a signal voltage. The Map sensor plays a very important roll for the Engine control unit.
The Map sensor can be found or fitted inside the Ecu, directly into the manifold or remote mounted with a vacuum pipe connected to the manifold.
Air flow/mass sensors (MAF)
The mass air flow sensor (MAF) is used to monitor the amount of air going into the engine while running. Mass air flow sensors work in conection with the oxygen sensor and the engine control system to give better performance and economy. A vehicles mass air flow sensor delivers a signal to the PCM computer(powertrain control module) telling the amount of air coming into the engine This is compared with oxygen levels in the exhaust to determine the efficiency of the engine. It is usually difficult to detect when a mass air flow sensor fails, the "check engine light" or engine symbol will probably not be illuminated. Your car, truck or SUV may have a poor idle quality, stall, low power or all three. Your PCM may have no trouble codes because the PCM cannot detect a problem since the sensor is working but is out of range.
What happens with most mass air flow sensor failures is the sensing element or "hot wire" that is used to give electronic feedback to the PCM for processing has become polluted by air . The mass air flow sensor is tells the PCM that less air is running through the engine than actually is. The PCM will then lean the fuel mixture down to the point that it will cause poor performance issues and it could lead to other problems.A mass air flow sensor is the most common in newer cars it used to maximize effenicay and reduce emission.
Vane or flap air flow sensor/meter (AFM)
The Mass Airflow sensor (Vane Type) is used to measure the amount of air going into the engine by means of a hinged Flap. It has the following parts.
Hinged Flap. This is connected to a potentiometer. The incoming air moves the flap and then this moves the contact along the potentiometer. The different resistance is converted into a signal voltage and then after that it is sent back to the Engine Control Unit.
Thermistor. This is used to measure the temperature of the incoming Air. The control unit tells the air temperature to signal voltage back to the Engine control unit.
Co-Potentiometer. mostly fitted to non catalyst cars. When fitted to cars with a catalytic converter it is normally factory sealed. By Adjusting this screw it alters the co signal voltage back to the Engine control unit. The Engine control unit it responds by altering the injection duration to either lean or richen the mixture.
Explain its internal operation and why your voltage changes:
When the amount of air intake changes the vane will move This vane changes the resistance and voltage when the vane is closes the resistance value is the highest with highest signal voltage (VS)
When the vane is fully opens the resistance value is the lowest with the lowest voltage.
Thermistor
Plot the resistance and temperature on the graph below
Temperature
here is some pictures i took when were testing them.
What type of thermistor is this?
NTC type ( negative temperature coefficient)
Explain the internal operation of the sensor?
The internal operation of the negative temperature sensor is when the temperature goes up the resistance will go down . Thermistor gets a decrease in electrical resistance when subjected to an increase in body temperature .
here is some pictures i took when were testing them cold.
References:
Way too much copy and paste. In class you hardly have done anything so how are able to explain everything in such great detail??
ReplyDelete