GM – CAMARO 1982-1992 – Repair Guide (Checked by WxMax) 547
EXHAUST GAS RECIRCULATION (EGR) SYSTEM
OPERATION
All models are equipped with
this system, which consists of a metering valve, a
vacuum line to the carburet or or intake manifold, and cast-in exhaust passages
in the intake manifold. The EGR valve is controlled by vacuum, which opens
and closes in response to the vacuum signals to admit exhaust gases into the
air/fuel mixture. The exhaust gases lower peak combustion temperatures,
reducing the formation of NOx. The valve is closed at idle and wide open
throttle, but is open between the two extreme positions.
There are actually four types of EGR systems: Ported, Positive Back-Pressure,
Negative Backpressure and Digital. The pr inciple of all the systems are the
same; the only difference is in the me thod used to control how the EGR valve
opens.
Too much EGR flow at idle, cruise or during cold operation may result in the
engine stalling after cold start, the engine stalling at idle after deceleration,
vehicle surge during cruise and rough idle . If the EGR valve is always open, the
vehicle may not idle. Too little or no EGR flow allows combustion temperatures
to rise, which could result in spar k knock (detonation), engine overheating
and/or emission test failure.
A Thermal Vacuum Switch (TVS) or vacuum control solenoid may sometimes\
be used in combination with the EGR va lve. The TVS will close off vacuum
during cold operation. A va cuum control solenoid uses Pulse Width Modulation
(PWM) to turn the solenoid ON and OFF numerous times a second and varies
the amount of ON time (pulse width) to vary the amount of ported vacuum
supplied the EGR valve.
PORTED VALVE
In the ported system, the amount of ex haust gas admitted into the intake
manifold depends on a ported vacuum signal. A ported vacuum signal is one
taken from the carburetor above the th rottle plates; thus, the vacuum signal
(amount of vacuum) is dependent on how far the throttle plates are opened.
When the throttle is closed (idle or dec eleration) there is no vacuum signal.
Thus, the EGR valve is closed, and no exhaust gas enters the intake mani\
fold.
As the throttle is opened, a vacuum is produced, which opens the EGR valve,
admitting exhaust gas into the intake manifold.
POSITIVE BACKPRE SSURE VALVE
This valve operates the same as the ported, except, it has an internal air bleed
that acts as a vacuum regulator. T he bleed valve controls the amount of
vacuum inside the vacuum chamber duri ng operation. When the valve receives
sufficient exhaust backpressure through the hollow shaft, it closes the bleed; at
this point the EGR valve opens.
GM – CAMARO 1982-1992 – Repair Guide (Checked by WxMax) 559
Fig. 14: Discard the old gasket. Be sure the remove all carbon deposits from the
ports on the EGR valve and the mounting surface
THERMOSTATIC AIR CLEANER (THERMAC)
OPERATION
This system is designed to warm the air entering the carburetor when
underhood temperatures are low, and to ma intain a controlled air temperature
into the carburetor or throttle body at all times. By allowing preheated air to
enter, the amount of time t he choke is on is reduced, resulting in better fuel
economy and lower emissions. Engine warm-up time is also reduced.
The THERMAC system is composed of th e air cleaner body, a filter, sensor
unit, vacuum diaphragm, damper door, a ssociated hoses and connections. Heat
radiating from the exhaust manifold is tr apped by a heat stove and is ducted to
the air cleaner to supply heated air to t he carburetor or throttle body. A movable
door in the air cleaner case snorkel allows air to be drawn in from the heat stove
(cold operation). The door position is co ntrolled by the vacuum motor, which
receives intake manifold vacuum as modulated by the temperature sensor.
A vacuum door which remain s open can cause carburetor icing or poor cold
driveability. A door which remains clos ed during normal engine operating
temperatures can cause sluggishne ss, engine knocking and overheating.
GM – CAMARO 1982-1992 – Repair Guide (Checked by WxMax) 784
b. If fluid is warm, the le
vel should be close to the ADD mark, either
above or below.
c. If fluid is too hot to touc h, the level should be at the FULL mark.
3. If the fluid level is low, add Dexr on®II automatic transmission fluid (ATF)
through the dipstick tube. This is eas ily done with the aid of a funnel.
Check the level often as you are f illing the transmission. Be extremely
careful not to overfill it. Overfilling will cause slippage, seal damage and
overheating. Approximately 1 pint (0.473L) of ATF will raise the fluid level
from one notch/line to the other.
If the fluid on the dipstick appears discolored (brown or black), or smells burnt,
serious transmission troubles, probably due to overheating, should be
suspected. The transmission should be inspected by a qualified technician to
locate the cause of the burnt fluid.
DRAIN AND REFILL
Please refer to the "PAN AND FILTER SERVICE" procedure listed in this
section.
PAN AND FILTER SERVICE
Fig. 2: Typical automatic transmiss ion oil pan and oil filter assembly.
Fig. 3: Automatic transmission oil pan bolt and conical washer assembly
