390 Auto Engine Performance and Driveability
Copyright by Goodheart-Willcox Co., Inc.
Checking the Thermostatic Air Cleaner
To check the operation of the thermostatic air cleaner,
observe the fl ap in the air cleaner snorkel when the engine
is off. It should be open. Attach a manual vacuum pump to
the air cleaner control vacuum hose. Apply vacuum to the
hose and observe the fl ap, Figure 18-25. The fl ap should
close. If it does not, the diaphragm is leaking or the control
valve is not working. To ensure that the fl ap is opening,
observe it after the engine is running at normal operating
temperature or heat the sensor with a heat gun. With the
vacuum hose connected to the manifold, the fl ap should
be completely open.
If the thermostatic air cleaner uses a heated element,
fi rst ensure that the element is cool. The fl ap should be
in the closed position, Figure 18-26. Then, heat the pellet
with a heat gun or allow the engine to warm it. The fl ap
should be open, Figure 18-27. If the fl ap does not operate
as specifi ed, the element is defective or the linkage is bent,
worn, or disconnected.
Checking Early Fuel Evaporation (EFE)
Systems
Two basic defects can occur on an early fuel evapora-
tion (EFE) system:
Sticking valve.
Problem with the vacuum-control system.
If the exhaust gases cause the valve to stick, it can usu-
ally be freed up by soaking the shaft with penetrating oil
and lightly tapping on the shaft. If a valve cannot be freed
or it keeps sticking, it should be replaced.
Problems with the EFE vacuum-control system can
be caused by a leaking vacuum diaphragm or failure of
the thermal vacuum valve and related hoses. First, make
a visual check of the vacuum lines to ensure they are not
split, collapsed, or disconnected. Then, remove the vacuum
line at the thermal vacuum valve and apply vacuum to the
diaphragm with a vacuum pump. If the valve is not stuck
and the diaphragm does not move, the diaphragm is defec-
tive. If the diaphragm moves when vacuum is applied with
the pump, but does not move when the engine is started
cold, the diaphragm is good and either the thermal vacuum
valve is defective or the hoses are misrouted.
Figure 18-23. Intrusive tests can determine if the solenoids are defective. Here, EGR solenoid 1 is being manually tested by the scan
tool. Idle speed should drop and the engine should run rough as each solenoid is tested.
Ignition timing (°BTDC) Base timing: 7 Actual timing: 21
Coolant temperature
sensor
211°F/99°C
Idle air control
valve
32 percent
Open/closed
loop
Closed
Fuel pump
relay
On
Malfunction indicator
lamp
Off
Diagnostic trouble
codes
Evaporative emission
canister solenoid
Off
Torque converter clutch
solenoid
Off
Data Scanned from Vehicle during Intrusive Test
EGR purge valve
0 percent
Intake air temperature
sensor
82°F/28°C
Manifold absolute pressure
sensor
.6 volts
Engine speed sensor
713 rpm
EGR solenoid 1
On
EGR solenoid 2
Off
EGR solenoid 3
Off
Knock signal
Yes
Vehicle speed sensor
0 mph
Oxygen sensor
.77 volts
Battery voltage
13.1 volts
Throttle position
sensor
.44 volts
Figure 18-24. Normal operation of the air pump muffl er is indi-
cated by a small amount of air exiting the muffl er. If air does not
exit, the diverter valve or pump is defective.