The TPS System

• Many people naturally associate the throttle position sensor (TPS) with how much fuel their engines are given, so they come to believe that the TPS system actually controls or delivers the fuel. This is not true. The intake manifold is the system that directly controls how much fuel is introduced into the engine with its manifold air pressure sensors. The TPS does, however, send data to the computer that will cause it to switch the air/fuel ratio for the engine in general.
  
  

Throttle Bodies vs. Carburetors

• Carburetors draw fuel into the engine by using changes in pressure through venturi, or constricted sections of pipe that control fuel flow and pressure. These venturi actually restrict air flow, which is necessary in a carburetor system that needs the pressure difference to provide enough force to inject the fuel. A throttle body, however, is used in a forced fuel injector system that does not need venturi, and can inject fuel with greater allowance for air flow, creating a wider range of engine capability.
  
  

Throttle Calibration

• Many people believe that manual throttle calibration is itself a myth, when in fact it can be very useful. Throttle calibration refers to the act of slowly easing up and down on the accelerator pedal while the engine is on in order to "set" the throttle and the signals it sends to the computer. With electronic throttle control systems, this can be effective. Essentially, the act helps coordinate the pedal sensor and the TB sensor, and depending on the computer can also help lead to more accurate readings of air/fuel ratios.
  
  

Throttles in Cold Weather

• Some throttle bodies are equipped with lines for coolant bypass. These were put into place by manufacturers like Dodge in case there was a danger of throttles freezing in cold weather. There have not actually been any reports of throttle bodies freezing in cold weather, and nearly all throttle bodies have been tested in sub-freezing conditions to make sure they still operate without flaws.
  
  

Cleaning

• While modern day fuel injection systems are very accurate and efficient, they can wear down over time. Throttle bodies can suffer from mild build-up due to the air flow. This build-up can, over time, affect throttle response and air intake. Every 75,000 miles or so it is wise to check or clean the inside of the throttle body, which can even be done at home with the proper know-how and spray cleaners. Throttle body cleaners are available at most auto parts stores, and instructions to take apart and clean the throttle can be found in maintenance manuals and online websites, such as the Mobil Oil site in Resources.