what is a throttle potenceometer

variable resistance tuning knob

Yes

Something that measures how much throttle you are giving an engine. It is a performance part that you could install on your car - but definetly not the first thing that should go on it.

It helps you get your drag race time down.

It sounds like you might mean a potentiometer. It is an electronic component that acts as a variable resistor. Usually, you twist it like a dial or slide it to allow increasing or decreasing amounts of electricity into the circuit, which means it functions as a throttle.

As always, Wikipedia: http://en.wikipedia.org/wiki/Potentiometer

Throttle position sensing device.
A potentiometer gives a changing potential/voltage depending on the position of rotation - volume controls etc are other examples. The ECU then makes decisions on the voltage output of the potentiometer, while checking all the other sensors as well.

A potentiometer is a variable-resistor, it could be used for feedback sensing, or graduated control of the throttle mechanism.

potentiometer; its like a variable rheostat, or adjustable electrical controller, for say, a model car. or my 400 amp welder has one to contro the powerflow.

a variable control

Either a tachometer or a horsepower measuring instrument. The new Bugatti has a guage to show output horsepower. That sounds like a potenceometer.

It sounds like someone is jerking your potenceometer.
New cars however have ''throttle by wire'' or called an electronic throttle - there is a servo that opens and closes the throttlebody - in the old days this was done via a cable that connected to the gas petal. Maybe that is what you're referring to.

A throttle potentiometer is a variable resistor mounted on the throttle body, the throttle pedal, or on the end of the throttle cable (on some cars with drive-by-wire throttling or fuel control).

It is used to sense how far you have pushed the throttle pedal, so that the engine management system can react to your actions.