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Perhaps the best advice as to removing the throttle position sensor is to not do so prematurely. With the unit in place, and the engine off, remove the plug attached to it, then measure the continuity between the center pin, and the two on either side. Next, ask an assistant to press down slightly on the accelerator pedal while you again measure the continuity. Finally, ask an assistant to press down on the accelerator pedal all the way, while you again measure the continuity. On some cars, the accelerator pedal and cable might be in bad shape, and it might make more sense to yank on the engine side of the accelerator cable, to simulate what your assistant might do.
If the throttle position sensor readings are different with the throttle closed vs. part-way open vs. all the way open, then the throttle position sensor is basically doing what it’s supposed to do.
A more crude yet logical-seeming check that I’ve read about is to unplug the connector at the throttle position sensor, while the engine is running. If the sound of the engine changes, it means the throttle position sensor was having an effect, which means it is basically functional as to the throttle-closed part of its function.
Although the throttle position sensor is important, my impression is that it won’t make a difference as to the engine totally failing to start or run.
The throttle position sensor is tricky to find because it is located underneath the throttle body.
The throttle cable end that is attached atop the motor rotates a shaft. Its position is sensed by the throttle position sensor. Following this logic should make it easier to locate the throttle position sensor.
The throttle position sensor attaches with two fasteners, typically screws. Its position is critical. When re-installing it, it’s a good idea to make sure that it senses when the throttle is fully closed and also when it is fully open. The resistance between the outgoing connectors can be measured, and it should change dramatically when the throttle moves to either of those two positions. With the engine not running, you should also be able to hear a slight “click” when the sensor reaches either of those two positions.
As a guideline for the new part, it might be wise to be aware of the position of the part being replaced, before it is removed.
I personally dislike working in awkward positions so I preferred to remove the entire throttle body so that I could take it indoors so as to have a good look at the throttle position sensor in a clean, brightly lighted environment.