Checking correct operation of the TPS sensor:
If you are suffering drivability issues at low speed, it is worth checking that the TPS (Throttle Position) sensor is working correctly.
The TPS sensor basically tells the ECU how far the throttle is open (how far the accelerator is pressed down) so that it knows how much fuel to inject. What can happen is that the sensor can move over time,
so that it sends the wrong information to the ECU, and usually results in the vehicle "jerking" on and off throttle at very low speed. Checking that the unit is correctly positioned and working properly is easy - the only tool you will need is a digital voltmeter. The test method is described below:
A = Throttle cam, B = Wiring connector, C = TPS
sensor (partly hidden)
1) Switch on the ignition, but don't start the engine.
2) Open the bonnet and locate the TPS sensor wiring connector. This is the brown plug behind the throttle cam, on the cabin side of the throttle body.
3) Set the voltmeter for DC voltage, and insert the probes into the top two wires on the wiring connector.
4) With the throttle in the idle position, you should get a reading of about 0.5 volts
5) If this is not the case, loosen the two bolts holding the TPS sensor in place, and twist round until you get the correct voltage reading.
6) Rotate the throttle cam and the voltage level should increase in proportion to the opening of the throttle.
7) When you twist the throttle cam as far as it will go (full throttle), you should get a
reading a little over 4 volts.
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