Volvo S70 Owner's Manual page 188

1999 S70 & V70
For proper functioning of the vehicle and its emission control systems, the fuel line filter should be
replaced at 105,000 miles (168,000 km). The filter is replaced as one complete unit. Replace more
frequently if contaminated fuel is introduced into the tank (or if there is reason to suspect that this has
occurred).
PCV system
The orifice nipple in the intake manifold and the filter at the end of the PCV hose in the air cleaner
should be inspected every 60,000 miles (96,000 km).
Cabin air filter
Replace the air cabin filter with a new one every 15,000 miles (24,000 km). Volvo recommends
replacing the filter more often if the car is driven under dirty and dusty conditions. The filter cannot be
cleaned and therefore should always be replaced with a new one.
pg. 122 Servicing (cont.)
Fuel System
The fuel system is all-electronic and is microprocessor-controlled. It can continually compensate for
variation in engine load, speed and temperature to give the best economy and power. A mass air flow
sensor measures the inducted air. In thisway 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 sensor monitors 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 (NOx) by a three-way catalytic converter.
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