Throttle Position Sensor

The throttle position sensor is responsible for monitoring where the throttle is positioned within the internal combustion engine. You can find the throttle position sensor attached to the butterfly spindle on most designs. By having the throttle position sensor on the butterfly spindle it will allow it to easily monitor where the throttle valve butterfly is positioned.

There are three different throttle position sensor designs. Your vehicle will have a potentiometer, switch, or combination design. While there are throttle position sensors for each of these designs, most vehicle's have the potentiometer design. Each type of throttle position sensor works efficiently but has a different way of functioning. You can find out more about these types of throttle sensors below.

Switch - designed to alternative between on and off when necessary. When the throttle is closed, it will be on, but when the vehicle is near idling, it will be off. The switch will turn back on once the throttle is widely opened. When the switch is off, your vehicle's computer system will be accepting data from other sensors to keep the vehicle driving properly and having a good throttle response.

Potentiometer – designed as a variable resistor which steadily increases the amount of voltage sent to the computer. The potentiometer design is effective because it follows the throttle which gradually opens so neither is activated before the other.

Combination – designed as a combination of the switch and potentiometer designs.
Throttle position sensors with the switch design can usually be adjusted, but that's not the case for the potentiometer design. Also, throttle position sensors with a combination of the two designs used to be adjustable but they’re now designed without the ability to be adjusted.

How the Throttle Position Sensor Works
The sensor coordinates with the engine control unit to make sure the throttle is always working proficiently. The throttle plays a major role in how your vehicle works (timing for your ignition and fuel injection) so it's important that it's always working. If your vehicle has a fuel injection engine you can prevent stalling by injecting extra fuel, which can be done by opening the throttle quickly.

The throttle position sensor will monitor the position of your vehicle's throttle valve. Whenever it's open or closed, the data is sent to the engine control unit. The data that gets sent to the engine control unit will help provide a quick response time whenever the amount of fuel being used has to change.

Signs of Bad Adjustment
It's important that the throttle position sensor is adjusted correctly. If the adjustment is off and the throttle plate is being opened too much, the sensor can't send data to the computer. There are signs of a bad adjustment that you should watch out for. You may start to notice that your vehicle stalls after starting, or is rough when idling. You may also even notice a ping in the engine. If there is poor adjustment then you likely won’t be able to use the diagnostic test within your vehicle or manage the ignition timing. These are all serious issues that would need to be resolved right away.

Repairing the Throttle Position Sensor
It's possible to fix the throttle position sensor if it's adjustable and you can set it back in place. However, this isn't always a workable solution. The main concern would be the throttle plate. Even if you adjust the sensor properly, the throttle plate would still be supplying too much air when the throttle is closed. Readjusting the throttle position sensor can lead to the idle air valve having its own set of problems.

If your throttle position sensor is not designed to be adjusted, you have to worry about the throttle cable as well. Repairing the throttle position sensor is definitely not an easy task and should be taken seriously. If you discover that there are problems with the throttle position sensor, seek help from a licensed, and reputable, auto mechanic immediately. Don't take the risk trying to fix it if you don't know what you’re doing as it could just lead to a new series of stressful repairs that are needed.

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  1. wow thanks! think you've solved my problem.When starting from cold the revs go from "normal" high to even higher before, at times, suddenly cutting out. If i do manage to keep it from stalling, the engine will sometimes cut out, just after moving off