CHEVROLET CAMARO 1982 Repair Guide

GM – CAMARO 1982-1992 – Repair Guide (Checked by WxMax) 541
EVAPORATIVE EMISS
ION CONTROLS
OPERATION
This system reduces the amount of gasoline vapors escaping into the
atmosphere. Some models em ploy a purge control solenoid which is controlled
by the ECM, to open and close the EE C system. Other models use a canister
mounted vacuum purge valve; when the engine vacuum reaches a certain
pressure, the valve opens allowing the gas vapors to be drawn off to the
carburetor for burning.
Carbureted models use an exhaust tube fr om the float bowl to the charcoal
canister; fuel injected models eliminate the fuel bowl tube (as no float bowl is
used on fuel injection systems). Fuel vapor s from the gas tank travel from the
tank to the vapor canister , where they are collected. Although the system varies
from vehicle-to-vehicle, the operat ions are basically the same.

Fig. 1: Evaporative Emission Cont rol (EEC) System - 2.5L engines

GM – CAMARO 1982-1992 – Repair Guide (Checked by WxMax) 542

Fig. 2: EEC system - 2.8L carbureted engines

GM – CAMARO 1982-1992 – Repair Guide (Checked by WxMax) 543

Fig. 3: EEC system on TPI and TBI V6/V8 engines

Fig. 4: EEC system on carbureted V8 engines

GM – CAMARO 1982-1992 – Repair Guide (Checked by WxMax) 544
TESTING
TANK PRESSURE CONTROL VALVE
1. Using a hand-held vacuum pump, apply a vacuum of 15 in. Hg. (51 kPa)
through the control vacuum signal tube to the purge valve diaphragm. If
the diaphragm does not hold 5 in. Hg . at least for 10 seconds, the
diaphragm is leaking. Repl ace the control valve.
2. With the vacuum still applied to t he control vacuum tube, attach a short
piece of hose to the valve's tank tube side and blow into the hose. Air \
should pass through the valve. If it does not, replace the control valve.
REMOVAL & INSTALLATION
CANISTER 1. Disconnect the negative battery cable.
2. Loosen the screw holding the c anister retaining bracket.
3. Remove the canister.
4. Tag and disconnect the hoses leading from the canister.
To install: 5. Connect the hoses to the cani ster according to the tags.
6. Install the canister into the retaining bracket.
7. Tighten the screw holding the c anister retaining bracket.
8. Reconnect the negative battery cable.

Fig. 5: A common EEC canister location

GM – CAMARO 1982-1992 – Repair Guide (Checked by WxMax) 545

Fig. 6: Be sure to label the hoses bef ore disconnecting them to avoid confusion
later
FILTER
Not all models use canister s with replaceable filters.
1. Remove the vapor canister.
2. Pull the filter out from the bottom of the canister.
3. Install a new filter and then replace the canister.
CANISTER PURGE SOLENOID 1. Disconnect the negative battery cable.
2. Remove the bolt, cover and solenoid.
3. Disconnect the electrical wirin g and hoses from the solenoid.
4. Remove the solenoid.
To install: 5. Install the solenoid, cover and bolt.
6. Connect the hoses and elec trical wiring solenoid.
7. Connect the negative battery cable.

GM – CAMARO 1982-1992 – Repair Guide (Checked by WxMax) 546

Fig. 7: A common canister purge solenoid location
TANK PRESSURE CONTROL VALVE 1. Disconnect the hoses fr om the control valve.
2. Remove the mounting hardware.
3. Remove the control valve from the vehicle.
4. Installation is the reverse of the re moval procedure. Refer to the Vehicle
Emission Control Information (VECI) label, located in the engine
compartment (if present) or the diagram s found later in this section, for
proper routing of the vacuum hoses.

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) 548
This valve will not open, wit
h vacuum applied to it, while the engine is idling or
stopped.

Fig. 1: Positive backpressure EGR valve
NEGATIVE BACKPRESSURE VALVE
This valve is similar to the positive ba ckpressure type, except, the bleed valve
spring is moved from above the diaphragm to below it. The bleed valve is
normally closed.
At certain manifold pressures, the EG R valve will open. When the manifold
vacuum combines with the negative exhaust backpressure, the bleed hole
opens and the EGR valve closes.
This valve will open when vacuum is applied and the engine is not running.

GM – CAMARO 1982-1992 – Repair Guide (Checked by WxMax) 549

Fig. 2: Negative backpressure EGR valve
DIGITAL EGR VALVE
The digital EGR valve, used on 3.1L (VIN T) engines, is designed to control the
flow of EGR independent of intake mani fold vacuum. The valve controls EGR
flow through 3 solenoid- opened orifices, which increa se in size, to produce 7
possible combinations. When a solenoid is energized, the armature with
attached shaft and swivel pintle, is lifted, opening the orifice.
The digital EGR valve is opened by t he ECM "quad-driver" (QDR), grounding
each solenoid circuit individually. The fl ow of EGR is regulated by the ECM
which uses information from the Coolant Temperature Sensor (CTS), Throttle
Position Sensor (TPS) and the Manifold Absolute Pressure (MAP) sensor to
determine the appropriate rate of flow for a particular engine operating
condition.

GM – CAMARO 1982-1992 – Repair Guide (Checked by WxMax) 550

Fig. 3: Digital EGR valve used on 3.1L engines

Fig. 4: Thermostatic Vacuum Sw itch (TVS) controlled EGR system