The throttle body is bolted straight onto the intake manifold and is the part where the air from the airfilter arrives before going into the intake manifold.

It houses the butterfly valve that controls the airflow into the intake manifold.

The throttle lever is operated with the accelerator pedal through a thin, steel cable. There is a thin rod attached to the throttle lever. There is a butterfly valve fixed to to that rod. The rod runs all the way through the opening of the throttle body. On the other end there is a TPS attached to it.

The TPS (Throttle Position Sensor) transmits the position of the throttle valve to the ECU. The ECU will take this value into account in it's calculations for the air/fuel mixture.

When the accelerator pedal (and thus the throttle valve) is operated, the valve will open and let more air enter the cylinders.

If the pedal isn't operated, the springs that you can see in the pictures, will force the valve shut. The throttle valve will then completely close off the main air entrance.

But off course we don't want the engine to stall due to air starvation when the valve is closed. When the engine is running stationary, the air is bypassed through the hole you can see in the picture, on the right side, just before the throttle valve.

This by-pass runs through the wall of the throttlebody housing and comes out on the other side of the throttle valve. It's an open connection, so there is always enough air going into the engine to support stationary rpm's. For the fine adjustment of the stationary rpm's, you can partially block off the bypass canal by a adjustment screw.

But when the engine makes a cold start, it always revs a little higher dan stationary to get the engine at normal operating temperatures. It takes a bit more air to let the engine rev higher for a short period.

For this purpose, Toyota created a second bypass. The entrance to this bypass can been seen on the bottom of the main air passage, just before the throttle valve.

This isn't a open passage, but there is a connection for coolant in the bottom end of the throttle body. There is a small thermostat in there that opens when the coolant is cold, and closes when the coolant is heating up.

That means that the air bypass is open at a cold start, some more air can enter the cylinders for a higher rpm. When the coolant reaches 80° Celcius, the thermostat will close the bypass and stationary rpm will drop to normal.

The vacuum connections speak for themselves. Because of the air rushing through the throttlebody, a vacuum is created (And that vacuum exists in the entire intakemanifold). This vacuum is used by various sensors, valves and other random parts.

Now only the throttle delay remains.

The throttle delay (sometimes also called dashpod) does exactly what the name implies.

When the throttle is closed, the throttle lever pushes against a little peg in the throttle delay. This little peg pushes against a membrame.

When the throttle is opend by the throttlecable and the lever releases the little peg, it is pushed back by a small spring and the membrame will suck air into the throttle delay.

When the throttle is closed again, the throttle lever will push the peg, spring and thus the membrame with it back again. The air will be forced out again, but because the air can't escape quick enough, it will act as an  cushen and dampen and slow down the last few millimeters of the throttle return.

This delay is needed when the throttle is suddenly released, to give the fuel mixture in the combustion chambers a chance to fully ignite en reduse the emissions of HC en CO gasses.