Requirements
Vehicle meets the requirement for exhaust emission. These vary
on the age and fuel type of the vehicle
Test procedure
The MOT inspection covers the vehicles emission levels. The
inspector will connect the car to a computer to take readings
from it's exhaust gasses.
The substances that are measured are carbon dioxide,
hydrocarbons and carbon monoxide. If any of these levels are
excessive then the MOT will be a failure.
Common faults
Emission control system component fault
Damaged or work emission control components can cause your
vehicle to fail it's MOT test. The emission control system is
largely responsible for the "breathing" of the engine.
The engine need to control the correct mixture of fuel to air in
order to burn the fuel correctly. If the vehicles emissions are
high them this may be due to a reduction in air flow. This could
be as simple as a blocked air filter, or as complicated as a
problem with the vehicles electronic brain.
Engine damage. Engine damage is a very
common cause of poor exhaust emissions. For example a blown
cylinder head gasket can lead to excessive oil consumption. This
in turn will lead to an increase in level of hydro carbons in
the exhaust emissions. The same result will be experienced with
various other engine component failures such as cylinder rings
or damaged pistons.
Catalytic converter. All modern cars are
required to be fitted with a catalytic converter, sometimes
referred to a catalyst or cat. The job of the catalytic
converter is to break down exhaust gasses to less dangerous
substances. If the catalytic converter is now working
effectively then it may cause an increase in dangerous emissions
to be released from your vehicle.
Also see: Exhaust
system
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inspection - Next Exhaust
system
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