1993 Volvo 960
Three-way Catalytic Converter
This is a supplementary device in the exhaust system, designed to clean exhaust gases. This device is
mainly a container with a ceramic material insert, designed to let the exhaust gases pass through
channels in the insert. The channel walls are covered by a thin layer of platinum-palladium. These
metals act as catalysts, permitting a chemical action to occur without actually taking part in it. The
emission (CO, HC, NOx) content will increase if the three-way catalytic converter is damaged. Vehicles
equipped with heated oxygen sensors use three-way catalytic converters containing platinum and
rhodium.
CAUTION:
Vehicles with a three-way catalytic converter must use unleaded fuel only. Otherwise the three-way
catalytic converter will become ineffective. See "Fuel requirements".
pg. 8:10 Servicing
Multiport Fuel Injection System (MFI)
MFI is all-electronic and microprocessor-controlled. It can continually compensate for variations in
engine load, speed and temperature to give the best economy and power. An important feature of the
system is a mass air flow sensor that measures the mass of the inducted air instead of the volume. In this
way the system can make instantaneous adjustments for changes in air temperature or density, thus
always assuring the best economy with the lowest possible exhaust emissions.
Heated oxygen sensor
This is an emission control system designed to reduce emissions and improve fuel economy. The heated
oxygen sensors monitor the composition of the exhaust gases leaving the engine. The exhaust gas
analysis is fed into an electronic module. This adjusts the air-fuel ratio to provide optimum conditions
for combustion and efficient reduction of the three major pollutants (hydrocarbons, carbon monoxide
and oxides of nitrogen) by a three-way catalytic converter.
Pulsed Secondary Air Injection (certain models)
This system adds air to the hot exhaust gases as they are expelled from the engine. This causes a
secondary combustion of residual hydrocarbons and carbon monoxide, resulting in lower emissions
levels in the exhaust gases.
pg. 8:11 Servicing
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