Is your fuel lean or
rich? Detect your car’s fuel efficiency with the help of Oxygen Sensors
available at parts avatar.
Every new car, mostly
after 1980s have an car oxygen sensor or O2 sensor. O2 sensors measure the amount of
oxygen in the exhaust gases and detects if the engine is running lean (not
enough fuel) or rich (too much fuel). To regulate engine performance and
efficiency, the computerized engine control system depends on the inputs from
these sensors. O2 sensors tell the car’s computer if it needs to add or take
away fuel. It also measures the efficiency of catalytic converter. The amount
of oxygen in the exhaust gas indicates good efficiency of engine combustion. A
gasoline engine burns gasoline in the presence of oxygen. Oxygen sensors are
located in exhaust manifold downpipes. It also does the job of checking air to
fuel ratio.
Temperature of air, engine, barometric pressure, load on an engine
and altitude can affect oxygen pulling efficiency of an engine. Therefore, we
would not know the exact air
to fuel ratio which would result in car’s poor
performance. That was why the oxygen sensors were designed.
Too much amount of oxygen
in the exhaust gases indicates a lean mixture. On the other hand too less
amount of oxygen indicates rich mixture. Both these circumstances affect fuel
efficiency. Lean mixture could damage an engine by increasing temperature of
engine and can ultimately lead to misfire. Rich mixtures reduce economy and
result in excess emissions.
Modern spark ignited
combustion engines use oxygen sensors and catalytic converters of cars
to reduce exhaust emissions.
HOW
IT WORKS?
An oxygen sensor
generates voltage signal proportional to amount of oxygen in the exhaust gas
and sends this signal to engine control unit i.e. ECU.
ECU maintains a certain air fuel ratio, by analyzing the information it gets
from O2 sensors.
The sensing element is
ceramic coated on both exhaust and reference sides with porous platinum
electrodes. Ceramic body is made of zirconium dioxide or zirconia. Rich mixture
causes oxygen demand. Due to transportation of oxygen ions into sensor, the
voltage builds up generally 0.8 to 0.9 volts. Lean mixture causes low voltage
generally 0.1 to 0.3 volts since there is excess level of oxygen.
Modifications that
alter the engine to act either too lean or too rich may result in inefficient
fuel consumption. So tampering with signals of O2 sensors could damage a
vehicle.
TYPES
OF OXYGEN SENSORS
Customers
should have a good knowledge of oxygen sensors in order to get correct oxygen
sensor fitting for their car.
ZIRCONIA SENSOR
It is most common
sensor and comes in both heated and unheated form. Its two electrodes provide
an output voltage proportional to quantity of oxygen in exhaust gases. It is
called a narrow band sensor because it can only detect a narrow band of air to
fuel ratio. It can either read lean or rich mixtures. Zirconia sensor is of two types:
1. Zirconia thimble
type
2. Zirconia thick film
type
TITANIUM DIOXIDE
It is less common type
of narrow band sensors called titanium dioxide sensors. It does not produce its
voltage but changes resistance in response to oxygen concentration. Its voltage
drop varies from 0 to 5 volts. They are expensive as compared to zirconia
sensors but their response time is also fast.
AIR FUEL RATIO SENSOR
Its work is similar to
that of an oxygen sensor, the difference being that the output signal is not
changed right after the mixture goes lean or rich. It is widely used in cars to
achieve better fuel economy and better engine performance. It not only tells
the ECU if the mixture is lean or rich but also tells how rich or how lean it
is. It is commonly used in after market high performance and driver air fuel
display equipment.
DIAGNOSING
THE SENSOR
There are a few things
to watch out before your O2 sensor fails.
1. The very first
affect of bad oxygen sensor is on fuel delivery and combustion system. The
incorrect measurement of air to fuel ratio may lead to reduced gas mileage of
your vehicle. If you need to fill your gas tank more than usual then get your
oxygen sensors checked by a professional.
2. A bad sensor could
affect air to fuel ratio and combustion intervals. This could lead to misfiring
of the engine.
3. Catalyst depletion
could cause the failure of heated sensors. Unheated sensors fail due to
building up of soot on ceramic element.
4. Lead, silicon, oil
ash or sulphur into the exhaust could damage the oxygen sensor. Some natural
elements like dirt, oil or water could also reduce efficiency of sensor.
5. Applying external
voltage to sensors could damage them.
6. Engine light would
illuminate if you have a failing sensor. Contact the professional as soon as
you detect this symptom.
7. If you detect rough
idling of engine and increased tailpipe emissions, then there may be something
wrong with your oxygen sensor. Get it checked.
REPLACING
THE SENSOR
If you are getting
consistent error codes from the computer, the sensor probably needs to be
changed. The sensor is a wear item and does fail over time. Replacement of bad
sensor will reduce the level of emission, restore fuel efficiency and increase
the life of converter. Unheated sensor can be replaced after 30000 to 50000
miles. A replacement interval of 100000
miles is recommended for heated or OBDII equipped vehicles.
You can visit Partsavatar.ca for good range
oxygen sensors.
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