Throttle body in gasoline engine
What does throttle body and how it works?
The
first part of a gasoline engine through which air is sucked in the engine is the throttlebody.
Engine
is basically an air pump. It sucks air, ignite fuel in it and discharge the air
through tail pipe. Throttle body is the essential part of a gasoline engine in
the air intake system where the throttle body controls the intake air to the
engine. A throttle body is a butterfly valve in a housing where it is mounted
on a shaft. The butterfly valve can be rotated through a mechanical linkage
cable or through a servo motor electrically. The motion of the butterfly valve
is registered to the ecu or car computer through a sensor known as throttle
position sensor or TPS.
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| Mechanical linkage type or old style throttle body |
When the gas pedal or accelerator pedal is pushed the butterfly or throttle
plate inside the throttle body is opened and allows the air to the engine
cylinder or combustion chamber. When the gas pedal is depressed, the butterfly
valve or the throttle plate closes and it restricts the air flow to the engine.
By this way the quantity of air is controlled to the engine and hence the
engine or vehicle speed is controlled.
How Throttle body Works
Throttle
body is located in between the air filter and air intake manifold of an engine.
The butterfly valve or the throttle plate inside the throttle body precisely control
the air intake to the engine. The quantity of the air regulates the air fuel
mixture to the gasoline engine. The engine needs air fuel mixture in a stoichiometry
level of 14.7:1 for proper ignition and optimum performance. If this stoichiometry
level is not maintained, the optimum operation and the performance can’t achieve.
Throttle body controls the air fuel ration very precisely all the time manually
by mechanical wire linkage or electronically through ecu or computer.
 |
| Motorized throttle body |
Idle air control value or IAC associated with throttle body
The
throttle body consists some more systems like IAC or idle air control valve
which is used to regulate the idle running of the vehicle. The IAC valve was
used on old style throttle bodies which were using a mechanical linkage cable
to activate the throttle plate or the butterfly plate inside the throttle body.
IAC valve or idle air control valve function is to retain the vehicle in start
condition at idle running conditions at 600 rpm all the time in all
circumstances. The IAC valve or the idle air control valve automatically
regulates the engine speed to 600 rpm when air conditioner compressor kicks on
and the vehicle is stopped at signals or in parking area start at idle speed
and people sitting inside.
 |
| IAC or Idle air control valve |
The
newer throttle bodies don’t use the mechanical linkage cable. Instead they use
a servo system controlled by engine control unit of ecu to regulate the air
intake through throttle body. These new throttle bodies controls or regulates
the air intake at idle through main throttle plate or butterfly valve. Their control
is very precise as in such new throttle bodies the throttle plate or the
butterfly valve is not directly controlled through the driver foot but it is controlled
by ecu or engine control module.
Problems with throttle body and their Solutions
Throttle body common defect is dust
accumulation inside the throttle body or the IAC valve or idle air control
valve. As 10000 liters of air is required to burn 1 liter of petrol. All this
air is passed through the throttle body. Although there is a filter located
before the throttle body but still air contains very fine particles of air
which could be accumulated inside the throttle body and they create issues in
air regulation especially idling become poor and rough if a throttle body
accumulated dust inside. The dust accumulation is not a very quick process and
it depends upon your environment where you drive your car and how often you
drive your can in routine. The solution to this problem is to clean and wash
the throttle body after certain period of time.
Other problem could be a worn out
throttle plate spindle bushings or bearings. In some cases there bushings could
be replaced and in most of the cases the whole throttle body is replaced with a
new one. Although this defect is very seldom and not very common.
In some cases you will see defective
temperature sensor at throttle body. The sensor could be failed sometimes due
to aging and mostly due to some other loose connection somewhere in the car
wiring. In such a case the sensor replacement and the loose connection repair
could solve the defect.
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