1988 PONTIAC FIERO Service Repair Manual

6E3-C6-8 2.8L (WIN S) DRIVEABILITY AND EMISSIONS
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DRIVEABILITY AND EMISSIONS 2.8L (VIN 5) 6E3-C7-1
SECTION C7
EXHAUST GAS RECIRCULATION (EGR) SYSTEM
CONTENTS
GENERAL DESCRIPTION ................ C7-1
PURPOSE
......................... C7-1
OPERATION
....................... C7-1
ELECTRONIC VACUUM REGULATOR
VALVE
........................... C7-1
PORT EGR VALVE
................... C7-2
EGR VALVE IDENTIFICATION..
......... C7-2
RESULTS OF INCORRECT OPERATION
... C7-2
DIAGNOSIS
......................... C7-3
GENERAL DESCRIPTION
PURPOSE
The EGR system is used to lower NO, (oxides of
nitrogen) emission levels caused by high combustion
temperature. It does this
by decreasing combustion
temperature.
The main element of the system is the
EGR valve
operated by vacuum and mounted
"ON" the intake
manifold.
The EGR valve feeds small
amounts of exhaust
gas back into the combustion chamber as shown in
Figure C7-1.
OPERATION
..................... ON-CAR SERVICE C7-3
EGR VALVE
........................ C7-3
EGR Manifold Passage
............... C7-3
EGR Manifold Passage
............... C7-4
ELECTRONIC VACUUM REGULATOR
VALVE
.......................... C7-4
EVRV FILTER REPLACEMENT
.......... C7-4
................. PARTS INFORMATION C7-4
EGR VALVE INTAKE AIR
1 EXHAUST GAS EGR VACUUM PORT I
The EGR valve is opened by vacuum to let exhaust
gas flow into the intake manifold.
l'he exhaust gas
then moves
witb the airlfuel mixture into the
combustion chamber. If too much exhaust gas enters,
combustion will not occur. For this reason, very little
exhaust gas is allowed to pass through the valve,
especially at idle. The
EGR valve is usually open
during warm engine operation and when the vehicle is
above idle speed.
The amount of exhaust gas recirculated is
controlled by variations in vacuum and the EGR
vacuum control solenoid.
ELECTRONIC VACUUM REGULATOR VALVE
The Electronic Vacuum Regulator Valve (EVRV)
uses "pulse width modulation" to control EGK flow.
This
means the ECM turns the solenoid "ON" and
"OFF many times a second and varies the amount of
"ON" time ("pulse width") to vary the amount ot'HGK.
Figure C7-1 Exhaust Gas Recirculation
The i1:CM uses information from the following
sensors to enable the EVRV:
@ Throttle position sensor ('I'PS)
@ Plh' Switch
Manifold
ahsolute temperature (MArI')
The ECM uses information from the following
sensors to regulate the EVRV:
@ Engine 1,oad
Coolant Temperature
@ 1)istributor (rpm Signal)
@ Torque Converter Clutch (TCC)
A diagnostic switch is part of the control and
monitors vacuum to the
EGK. valve. 'I'his switch will
trigger a "Service Engine Soon" light, and set a Code
ai ure. 32 in the event of a vacuum circuit f 'I

EXHAUST GAS VALVE OPEN
INTAKE AIR
171 VALVE CLOSED
VACUUM PORT
/ SPRING 4s 05366E
Figure C7-2 - Port EGR Valve
PORT EGR VALVE
The port EGR valve (Figure C7-2) is controlled by
a flexible diaphragm which is spring loaded to hold
the valve closed. Ported vacuum applied to the top
side of the diaphragm overcomes the spring pressure
and opens the valve in the exhaust gas port. This
allows exhaust gas to be pulled into the intake
manifold and enter the engine cylinders.
* 45 0538-6E 2-27-87
Figure C7-4 - EGR Valve Identification
Too little or no EGR flow allows combustion
temperatures to get too high during acceleration and
load conditions. This could cause:
@ Spark knock (detonation).
@ Engine overheating.
@ Emission test failure.
Diagnosis of the EGR system is covered in CHART
C-7 for the 2.8L at the end of this section.
EGR VALVE IDENTIFICATION
ON-CAR SERVICE @ Negative backpressure EGR valves will have an
"N" stamped on the top side of the valve after the
part number (Figure
C7-4).
Positive backpressure EGR valves will have a "P"
stamped on the top side of the valve, after the part
number.
@ Port EGR valves have no identification stamped
after the part number.
When replacing an EGR valve, always check for
correct part number in the parts catalog or
supplemental bulletin.
RESULTS OF INCORRECT OPERATION
Too much EGR flow tends to weaken combustion,
causing the engine to run roughly or stop. With too
much EGR flow at idle, cruise, or cold operation, any
of the following conditions may happen:
@ Engine stops after cold start.
e Engine stops at idle after deceleration.
@ Car surges during cruise.
@ Rough idle.
If the EGR valve should stay open
a11 of the time,
the engine may not idle.
EGR VALVE
Remove or Disconnect
1. Vacuum line
2. Bolts
3. EGRvalve
Install or Connect
1. EGR valve
2. Bolts
3. Vacuum line
EGR Manifold Passage
Inspect
If EGR passages in the inlet manifold indicate
excessive build-up of deposits, the passages should be
cleaned. Care should be taken to ensure that all loose
particles are completely removed to prevent them
from clogging the EGR valve or from being ingested
into the engine.

DRIVEABILITY AND EMISSIONS 2.8L (VIM 5) 6E3-C7-3
- Figure C7-5 - EGR to Manifold Mounting
Do not wash EGR valve in solvents or degreaser--
permanent damage to valve diaphragm
may result.
Also sand blasting of the valve is not recommended,
since this can affect the operation of the valve.
1. With a wire wheel, buff the exhaust deposits fro111
the mounting surface and around the valve.
2. Look for exhaust deposits in the valve outlet.
Remove deposit build-up with a screwdriver.
3. Clean mounting surfaces of intake manifold and
valve assembly.
EGR Manifold Passage
a Inspect
If EGR passages in the inlet manifold indicate
excessive build-up of deposits, the passages should be
cleaned. Care should be taken to ensure that
a11 loose
particles are completely removed to prevent them
from clogging the
EGR valve or from being ingested
into the engine.
Do not wash
EGR valve in solvents or clegrcaser--
permanent damage to valve diaphragm may result.
Also, sand blasting of the valve is
not 1.ccomrnendec1
since this can affect the operation of the villve
Clean
1. With a wire wheel, buff the exhaust deposits from
the mounting surface and around the valve.
2. Look for exhaust deposits in the valve outlet.
Remove deposit build-up with a screwdriver.
3. Clean mounting surfaces of intake manifold and
valve assembly.
EGR CONTROL ~EGR DIAGNOSTIC SOLENOID VACUUM SWITCH
Figure C7-6 - EGR Control Solenoid
( EGR VACUUM CONTROL
ASSEMBLY BASE
( EGR VACUUM DIAGNOSTIC SWITCH
1 DIAGNOSTIC SWITCH CONNECTORS
1 EGR SOLENOID
FILTER
45 1182-6EA
Figure C7-7 - EGR Vacuum Control Assembly

ELECTRONIC VACUUM REGULATOR VALVE
Remove or Disconnect
1. Negative battery cable.
2, Electrical connector at regulator valve
3. Vacuum hoses.
4. Nut and regulator valve.
Install or Connect
1. Regulator valve and bracket, tighten nut to
24 N . m (17 lb. ft.).
2. Vacuum hoses
3. Electrical connector
4. Negative battery cable
EVRV FILTER REPLACEMENT
The EVRV filter should be replaced every 30, 000
miles.
1. Grasp and pull filter "OFF" with a rocking motion.
2. Push A ew filter "ON", making sure cut-out for
wires is properly aligned.
PARTS INFORMATION
PARTS NAME GROUP
........................ Valve, ECR :; ri70
.................. Gasket, EGIt VaI~re ;I (i8O
................ Control, EGR Vacuium :i.i;i'O

BLANK

6E3-C7-6 2.8L (VIN S) DRIWEABIILBTY AND EMISSIONS
I.P. CONN. "G'
450 BLWWHT
CHART C-7
EXHAUST GAS RECIRCULATION CHECK
2.$h (VIN %) ""F-SERIES (PORT)
Circuit Description:
The EGR valve is controlled by a normally closed solenoid (allow a vacuum to pass when energized). 'I'he
ECM energizes the solenoid to turn the EGR "ON", and monitors vacuum to the EGR with the EGR diagnostic
switch. Code
32 will detect a faulty solenoid, vacuum switch or vacuum supply. CIIART C-7 checks for plugged
EGR passages, a sticking EGR valve, or
n stuck open solenoid.
Test Description: Numbers below refer to circled 3. Checks for pluged EGR passLlges. If passages are
numbers on the diagnostic chart.
plugged, the engine may have severe deton
a t' lon on
1. With the ignition "ON" engine stopped, the
acceleration.
solenoid should not be energized and vacuum
4. The EGR solenoid will not be energized in Park or
should not pass to the EGR valve. Neutral. This test will determine if the
2. Grounding the diagnostic terminal will energize Pal.k/Neutral switch input is being received by the
the solenoid and allow vacuum to pass to valve.
ECM.

DRIVEABILITY AND EMISSIONS 2.8L (WIN S) 6E3-C7-7
CHART &-7
ASSUMES NO CODE 32 IS STORED
@ DISCONNECT EGR SOLENOID VACUUM HARNESS.
ROTATE HARNESS AND REINSTALL ONLY THE EGR VALVE SIDE.
@ CHECK PORTED VACUUM SOURCE TO SOLENOID ( IF NOT OK, REPAlR ). @ INSTALL A HAND HELD VACUUM PUMP WITH GAGE ON MANIFOLD SIDE
OF EGR SOLENOID.
@a IGNITION "ON", ENGINE STOPPED. @ DIAGNOSTIC TERMINAL NOT GROUNDED. @ APPLY VACUUM. @a OSBSERVE EGR VALVE.
REPLACE EGR
CHECK
CKT435 FOR SHORT TO GROUND. IF MOT SHORTED, IT IS FAULTY ECM. SEE ECM QUAD
@ CHECK PASSAGES FOR BEING PLUGGED.
IF NOT PLUGGED REPLACE EGR VALVE.
REPLACE EGR
VACUUM LINES, PERFORM
PIN SWITCH CHECK. CHART C-1A A,'T