Crankcase Emission Control System; General Precautions - Subaru SVX 1992 Manual

2-1 103A01 EMISSION CONTROL SYSTEM AND VACUUM FITTING
3. General Precautions
1) Know the importance of periodic maintenance ser-
vices .
(1) Every service item in the periodic maintenance
schedule must be performed .
(2) Failing to do even one item can cause the engine
to run poorly and increase exhaust emissions.
2) Determine if you have an engine or emission system
problem .
(1) Engine problems are usually not caused by the
emission control systems .
(2) When troubleshooting, always check the engine
and the MPFI system first.
3) Check hose and wiring connections first.
The most frequent cause of problems is simply a bad
connection in the wiring or vacuum hoses . Always make
sure that connections are secure and correct .
4) Avoid coasting with the ignition turned off and pro-
longed engine braking.
5) Do not damage parts .
(1) To disconnect vacuum hoses, pull on the end, not
the middle of the hose.
(2) To pull apart electrical connectors, pull on the
connector itself, not the wire.
(3) Be careful not to drop electrical parts, such as
sensors, or relays.
If they are dropped on a hard floor, they should be
replaced and not reused .
(4) When checking continuity at the wire connector,
the test bar should be inserted carefully to prevent
terminals from bending .
6) Use SUBARU genuine parts .
7) Record how hoses are connected before discon-
necting .
(1) When disconnecting vacuum hoses, use tags to
identify how they should be reconnected .
(2) After completing a job, double check to see that
the vacuum hoses are properly connected . See the
"Vacuum connections label" under the hood .
4. Crankcase Emission Control
System
A: DESCRIPTION
The positive crankcase ventilation (PCV) system is em-
ployed to prevent air pollution which will be caused by
blow-by gas being emitted from the crankcase .
The system consists of a sealed oil filler cap, rocker
covers with fresh air inlet, connecting hoses, PCV valve
and an air intake duct.
At the part throttle, the blow-by gas in the crankcase
flows into the intake manifold through the connecting
hose of crank case and PCV valve by the strong vacuum
of the intake manifold . Under this condition, the fresh air
is introduced into the crankcase through connecting
hose of rocker cover.
At wide open throttle, a part of blow-by gas flows into
the air intake duct through the connecting hose and is
drawn to the throttle chamber, because under this
condition, the intake manifold vacuum is not so strong
as to introduce all blow-by gases increasing with engine
speed directly through the PCV valve.
---+ Fresh air
--+ Mixture of air
Air intake duct
and blow-by gas
--i Blow-by gas
Throttle body
PCV valve
T
0
Cylinder head
Cylinder block
C2-050
Fig . 2
4