1988 PONTIAC FIERO Service Repair Manual

6E2-C6-6 DRIVEABILITY AND EMISSIONS - 5.OL (VIN E)
A.I.W. CONVERTER SOL.
CONNECTORS
429 BLWPNK
CONNECTOR CONNECTOR
CHART C-6
AIR MAMAGEMENKHECM - PEDES VALVE
(PRESSURE OPERATED ELECTRlC DIVERVELECTRIC SWITCHING)
5.Qb (VIN E) ""FYSERIES (TBI)
Circuit Description:
Air management is controlled by a port valve and a converter valve, each with an ECM controlled vacuum
solenoid. When the solenoid is grounded by the ECM,
AIR pressure will activate the valve and allow pump air
to be directed as follows:
Neither solenoid grounded by the
ECM - Air pump air diverted to atmosphere. Converter solenoid grounded
by the
ECIM - Air pump air to converter.
Port solenoid grounded by the ECM
- Air pump air to exhaust ports.
Test Description: Numbers below refer to circled
numbers on the diagnostic chart.
I. This is a system functional check. Air is directed
to ports during "Open Loop" and all engine start in
"Open Loop" even on a warm engine. Since the air
to the ports time is very short on some engines,
prepare to observe port air prior to engine start up.
On some engines, this can be done by squeezing a
hose. On others, steel pipes have
to be
disconnected.
2. This should normally set a Code 22. When any
code is set, the
ECM opens the ground to the air
control valve and allows air to divert. This checks
for
ECM response to a fault. A ground in the
control valve circuit to the ECM would prevent
divert action.
3. This checks for a grounded circuit to the ECM.
Test light
"OFF" is normal and would indicate the
circuit
is not grounded.
4. Checks for an open in the solenoid control circuits.
Grounding the test terminal should ground both
solenoid circuits. Normally, the test light should
be "ON" which indicates the problem is not in the
ECM or wiring but at the solenoid connections or
valve itself.
5. Checks for a grounded switching valve circuit.
Test light "OFF" would indicate the circuit is
normal and fault is in the valve.

DRIVEABILITY AND EMISSIONS 5.0b (VIN E) 6EZ-C6-7
CHART C-6
"DIAGNOSTIC" T PORT VALVE
GHf BETWEEN
CTOR TERMINALS

6EZ-C6-8 5.OL (VIN E) DRIVEABILITY AND EMISSIONS
BLANK

DRIVEABILITY AND EMISSIONS - 5.OL (VIN E) 6E2-C7-1
SECTION C7
EXHAUST GAS RECIRCULAVON (EGR) SYSEENO
GENERAL DESCRIPTION ...............
........................ PURPOSE
OPERATION
......................
EGR CONTROL .....................
...... NEGATIVE BACKPRESSURE VALVE
.......... EGR VALVE IDENTIFICATION
RESULTS OF INCORRECT OPERATION
. . , .
CONTENTS
......................... C7-1 DIAGNOSIS C7-2
..................... C7-1 ON-CAR SERVICE C7-2
....................... C7-1 EGRVALVE C7-2
............. C7-1 EGR Manifold Passage C7-2
C7-1
EGR CONTROL SOLENOID ............. C7-3
C7-2 PARTS INFORMATION
................. C7-3
C7-2
GENERAL DESCRIPTION
PURPOSE
The EGR system is used to lower NO, (oxides of
nitrogen) emission levels caused by high combustion
temperatures.
It does this by decreasing combustion
temperature. The main element of the system is an
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
The EGR valve is opened by manifold vacuum
regulated by an ECM controlled solenoid to let
exhaust gas flow into the intake manifold. The
exhaust gas then moves with 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.
EGR CONTROL
The EGR vacuum control has a vacuum solenoid
that uses "pulse width modulation". 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 of EGR.
The ECM uses information from the following
sensors to regulate the EGR solenoid:
@ Coolant Temperature
@ Throttle Position (TPS)
PIN Switch
T'IT] EGR VALVE a INTAKE AIR
EXHAUST GAS
a EGR VACUUM PORT
45 0001 -6E
Figure C7-1 - Exhaust Gas Recirculation
During cold operation and at idle, the solenoid
circuit is not grounded by the ECM.
'I'his blocks
vacuum to the EGR valve.
A system malfunction should trigger a "Service
Engine Soon" light, and set a Code
32. For more
information see Code
CHAR'I' 32.
NEGATIVE BACKPRESSURE VALVE
The valve used on this,engine is a negative
backpressure valve. It varies the amount of eshaust
gas flow into the manifold depending on manifold
vacuum and variations in exhaust backpressure.
The diaphragm on this valve (shown in Figure
C7-
2) has an internal vacuum bleed hole which is held
closed by a sinall spring when there is no eshaust
backpressure.
The amount of vacuum to the valve is
controlled
by the ECM controlling a solenoid.
Engine vacuum opens the EGR valve against
the
pressure of a large spring. When manifold vacuum
combines with negative exhaust backpressure, the
vacuum bleed hole opens and the EGR valve closes

6E2-C7-2 DRlVEABlLlTV AND EMISSIONS - 5.OL
EGR VALVE AIR BLEED
EXHAUST GAS HOLE
1 INTAKE
AIR SMALL SPRING
1 VACUUM PORT LARGE SPRING
DIAPHRAGM
45 01 13-61
Figure C7-2 - Negative Backpressure EGR Valve
EGR VALVE IDENTIFICATION
@ Negative backpressure EGR valves will have an
"N" stamped on the top side of the valve after the
part number (Figure
C7-3).
@ 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 (at idle, cruise, or cold
operation) and may result in any of the following
conditions:
- Engine stops after cold start.
- Engine stops at idle after deceleration.
- Car surges during cruise.
- Rough idle.
Too little or no EGR flow allows combustion
temperatures to get too high during acceleration and
load conditions. This could causes:
- Spark knock (detonation).
- Engine overheating.
- Emission test failure.
Figure C7-3 - EGR Valve Identification
DIAGNOSIS
Diagnosis of the ECM controlled EGR system on
the
5.OL is covered in CHART C-7 at the end of this
section. If the vehicle has
a stored Code 32 see that
chart first.
ON-CAR SERVICE
ECR VALVE
Remove or Disconnect
1. Air cleaner.
2. EGR valve vacuum hose at valve.
3. Bolts.
4. EGR valve from manifold.
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.
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.

DRIVEABILITY AND EMISSIONS - 5.OL (VIN E) 6EZ-C7-3
EGR CONTROL SOLENOID
Install or Connect
1, EGR valve on intake manifold using new gasket.
2. Bolts and tighten to 22 N . m (16 lb. ft.).
3. Vacuum hose to valve.
4. Air cleaner.
EGR VALVE
GASKET
13] BOLT (2) 85 4417-6
Figure C7-4 - EGR to Manifold Mounting 5.OL
( EGR SOLENOID ( BOLT 14-20 Narn (10-14 FT. LBS.)
Remove or Disconnect
1. Negative battery cable.
2. Air cleaner.
3. Electrical connector at solenoid,
(Figure
C7-4)
4. Vacuum hoses.
5. Nut and solenoid.
a lnstall or Connect
1. Solenoid and bracket. Tighten nut to 24 N . m
(17 lb. ft.).
2. Vacuum hoses.
3. Electrical connector.
4. Air cleaner.
5. Negative battery cable.
PARTS INFORMATION
PART NAME GROUP
...................... Valve, EGR 3.670
.......... Solenoid, EGR Cont Vlv Rly 3.670
................. Gasket, EGR Valve 3.680
Figure C7-5 - EGR Control Solenoid 5.OL

6E2-C7-4 DRIVEABILITY AND EMISSIONS - 5.OL (VIN E)
TO EGR VALVE
EGR SOLENOID
CHART C-7
EXHAUST GAS RECIRULATIOM (EGR) CHECK
5.QL (VIN E) "F" "SERIES (TBI)
Circuit Description :
The ECM operates a solenoid to control the exhaust gas recirculation (EGR) valve. This
solenoid is
normally closed. By providing a ground path, the ECN energizes the solenoid which then allows vacuum to pass
to the EGR valve. The
ECM control of the EGR is based on the following inputs:
@ Engine coolant temperature - above 25°C.
@ TPS - off idle
@ MAP
If Code 24 is stored, use that chart first.
Test Description: Numbers below refer to circled
numbers on the diagnostic chart.
1. Checks for solenoid stuck open.
2. Checks for solenoid always being energized.
3. Grounding test terminal will energize the solenoid
and vacuum will drop.
4. Negative backpressure valve should hold vacuum
with engine
"OFF".
5. When engine is started, exhaust backpressure
should cause vacuum to bleed off and valve to fully
close.
6. 5.OL engines have a manifold vacuum source
which should have at least
7 hg at idle.

DRIVEABILITY AND EMISSIONS - 5.OL (WIN E) 6E2-C7-5
SHOULD BE AT LEAST (7") HG VACUUM AT 2000 RPM.
SIDE OF EGR SOLENOID.
APPLY VACUUM AND OBSERVE VALVE.
OBSERVE EGR
DIAPHRAGM WHILE
APPLYING VACUUM.
DIAPHRAGM SHOULD
MOVE FREELY AND
HOLD VACUUM FOR AT
LEAST
20 SECONDS.
@ START ENGINE AND IMMEDIATELY
OBSERVE VACUUM GAGE ON
VACUUM PUMP.
@ VALVE IS GOOD IF DIAPHRAGM
HAS MOVED TO SEATED POSITION
(VALVE CLOSED) AND VACUUM
DROPPED WHILE STARTING
M HOSE BETWEEN
EGR VALVE IS OK.
ESTRICTIONS) IF FOUND, THE EGR