Volvo S40 - Manual (Page 146)

2003 Volvo S40 & V40
variation in engine load, speed and temperature to give the best economy and power. A mass air flow
sensor measures the inducted air. 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 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.
Crankcase ventilation
The engine is provided with positive crankcase ventilation which prevents crankcase gases from being
released into the atmosphere. Instead, the crankcase gases are admitted to the intake manifold and
cylinders.
Evaporative control system
The car is equipped with an evaporative control system which prevents gasoline vapor from being
released into the atmosphere.
The system consists of a fuel tank with filler pipe and cap, a rollover valve, a Fill Limit Vent Valve
(FLVV), vapor vent lines, a charcoal canister, a purge line, a purge control valve and engine
connections. In addition, there is a pressure sensor connected to the fuel tank and a filter-protected
Canister Close Valve (CCV) on the atmospheric side of the canister, for system diagnosis.
The gasoline vapor is channeled through the rollover valve and the FLVV via the vapor vent lines into
the charcoal canister, where it is stored. When the engine is started, the gasoline vapor is drawn from the
charcoal canister to the engine's air intake system and into the combustion process.
NOTE:
●
If the fuel filler cap is not closed tightly or if the engine is running when the car is refueled, the Check
Engine light may illuminate.
●
During a transitional period, a small number of service stations may still have fuel nozzles that are not
compatible with the fuel filler neck on cars equipped with the evaporative emission control system
mandated by the U.S. Environmental Protection Agency and the California Air Resources Board. If you
experience difficulties in refueling your vehicle, please ask the gas station attendant for assistance.
CAUTION:
Fuel must not be siphoned from the fuel tank. This will damage the evaporative emission control system.
file:///K|/ownersdocs/2003/2003_SV40/03sv40_08a.htm (7 of 8)12/30/2006 4:16:13 PM