All gasoline-powered vehicles need to take in air to function properly. The air is mixed with gasoline in the combustion chamber, and a precise ratio is needed for optimal performance. The throttle controls how much air is let into the engine based on how much pressure the driver puts on the gas pedal.

Internal combustion engines that use direct injection have a throttle body to control the air intake that is typically located between the air filter and the intake manifold. When the driver steps on the accelerator, a blade opens on the throttle body that allows air to pass through into the intake manifold.

This component of the engine's air intake system needs to be cleaned regularly to function efficiently when fuel-injected engines get older. They tend to be self-sufficient for the first few years, but typically need regular servicing and maintenance after 75,000 miles.

When the throttle body is dirty, it can cause the engine to run roughly when idling. The car may also stall or have difficulty accelerating, even after the engine is warmed up.

Cleaning this component of the car requires a few basic tools - a flat or Philips-head screwdriver, a socket wrench and a small soft-bristle brush. You will also need special throttle body cleaner, paper towels, rubber gloves and protective eyewear. Throttle body cleaner is a potent mixture of chemicals, which is why it is important that drivers embark on this cleaning project outside so there is plenty of fresh air.

Before beginning this project, it is wise to disconnect the negative terminal of the car's battery as a precautionary measure. You will also want to make sure to properly label the hoses and couplings that connect to the throttle body before you disconnect them to make it easier to put things back together when the project is complete. Small hoses should be disconnected, but any wires or terminals should be left alone.

If the throttle body is connected to air ducts on both sides, you will only need to detach one side to gain access for cleaning. Some hoses will be simply pressed into place and require a bit of wiggling to be removed. Others may require the use of a screwdriver or socket wrench.

Spray the cleaner into the opening of the throttle body, and use the cleaning brush to gently scrub away any buildup of gum, dirt and varnish that may be present. Be careful not to let anything fall into the opening of the throttle body. Wipe away any excess cleaning product with the paper towels and repeat this process until the metal of the interior surfaces is exposed.

Once the air duct is clean, apply a dab of oil to the throttle shaft before reconnecting the throttle body so the blade can open and close easily. Then you can reattach the hoses, making sure to tighten the clamps to approximately the same tightness they were when you removed them.

After the throttle body is reattached, you can reconnect the battery and fire up the engine. It may run rough at first while any cleaning residue is burned off. This may also cause the exhaust smoke to be white. After letting the engine idle for a few minutes, take the car for a test drive. If the engine was running rough before, it should be a bit smoother now. However, even if you don't notice a difference in the engine's performance, cleaning the throttle body is a great way to prevent problems from occurring in the first place.