1988 PONTIAC FIERO fuel pump

&E3-B-4 %.8L (VIN S) DRIVEABILITY AND EMISSIONS
LACK OF POWER, SLUGGISH, OR SPONGY
Definition: Engine delivers less than expected power. Little or
no increase in speed when accelerator pedal is pushed down part way.
Perform careful visual check as described at
- EGR operation for being open or partly open all
start of Section
"B". the time - CHART C-7.
e Compare customer's car to similar unit. - Exhaust system for possible restriction: See
Make sure the customer's car has an actual CHART
B-1,
problem.
@ Remove air cleaner and check air filter for
dirt, or for being plugged. Replace as
necessary.
@ CHECK:
- For loose or leaking air duct between MAF
Sensor and throttle body.
- Ignition timing. See Emission Control
Information label.
- Restricted fuel filter, contaminated fuel or
improper fuel pressure. See CHART A-7.
- ECM ground circuits - See ECM wiring
diagrams.
- Inspect exhaust system for damaged or
collapsed pipes.
- Inspect muffler for heat distress or possible
internal failure.
- Generator output voltage. Repair if less than 9
or more than 16 volts.
- Engine valve timing and compression.
- Engine for proper or worn camshaft. See
Section
"6A".
- Secondary voltage using a shop ocilliscope or a
spark tester
5-26792 (ST-125) or equivalent.
DETONATION ISPARK KNOCK
Definition: A mild to severe ping, usually worse under
acceleration. The engine makes sharp metallic knocks that
change with throttle opening. Sounds like popcorn popping.
@ Check for obvious overheating problems:
- Low coolant.
- Loose water pump belt.
- Restricted air flow to radiator, or restricted
water flow thru radiator.
- Inoperative electric cooling fan circuit. See
CHART C-12.
@ CHECK:
- Ignition timing. See Vehicle Emission
Control Information label.
- EGR system for not opening - CHART C-7.
- TCC operation - CHART C-8.
- Fuel system pressure. See CHART A-7.
- PROM or MEM-CAL - Be sure it's the correct
one. (See Service Bulletins)
- Valve oil seals for leaking.
@ Check for incorrect basic engine parts such as
cam, heads, pistons, etc.
@ Check for poor fuel quality.
@ Remove carbon with top engine cleaner. Follow
instructions on can.
@ Check ESC system (5.OL & 5.7L)
See CHART C-5
o To help determine if the condition is caused by a
rich or lean system, the car should be driven at
the speed of the complaint.
Monitoring block
learn at the complaint speed will help identify the
cause of the problem.
If the system is runnig lean
(block learn greater than
1381, refer to
"Diagnostic Aids" on facing page of Code 44.
If
the system is running rich (block learn less than
l18), refer to "Diagnostic Aids" on facing page of
Code 45.

CHART B-l
RESTRICTED EXHAUST SYSEEM CHECK
ALL ENGINES
Proper diagnosis for a restricted exhaust system is essential before any components are replaced. Either of
the following procedures may be used for diagnosis, depending upon engine or tool used:
CHECK AT A. I. R. PIPE: - OR
1. Remove the rubber hose at the exhaust
manifold A.I.R. pipe check valve. Remove
check valve.
2. Connect a fuel pump pressure gauge to a hose
and nipple from a Propane Enrichment
Device (526911) (see illustration).
3. Insert the nipple into the exhaust manifold
A.I.R. pipe.
GAGE
1 HOSE AND NIPPLE ADAPTER
1 3,I.R. PIPE (EXHAUST PORT)
1 CHECK VALVE 7s 3363-6E
CHECK AT 02 SENSOR:
1. Carefully remove 02 sensor.
2. Install Borroughs Exhaust Backpressure
Tester (BT 8515 or BT 8603) or equivalent in
place of
02 sensor (see illustration).
3. After
completing test described below, be
sure to coat threads of
02 sensor with anti-
seize compound PIN 5613695 or equivalent
prior to re-installation.
DIAGNOSIS:
1. With the engine idling at normal operating temperature, observe the exhaust system backpressure
reading on the gauge. Reading should not exceed
I $ psi (8.6 kPa).
2. Accelerate engine to 2000 RPM and observe gauge. Reading should not exceed 3 psi (20.7 kPa).
3. If the backpressure, at either RPM, exceeds specification, a restricted exhaust system is indicated.
4. Inspect the entire exhaust system for a collapsed pipe, heat distress, or possible internal muffler failure.
5. If
there are no obvious reasons for the excessive backpressure,
a restricted catalytic converter should be
suspected and replaced using current
recom~nended procedures.

6E3-(31-8 2.8L (VIN S) DRIVEABILITY AND EMISSIONS
( MASS AIR FLOW SENSOR
Figure C1-10 MAF Sensor Service
BRAKE BOOSTER FUEL PUMP RELAY
/ /FAN RELAY
FORWARD LAMP
/ BULKHEAD
Figure C1-I I Relays
OXYGEN SENSOR
NOTICE:
The oxygen sensor uses a permanently
attached pigtail and connector. This
pigtail should not be removed from the
oxygen sensor. Damage or removal of the
pigtail or connector could affect proper
operation of the oxygen sensor.
Important
Take care when handling the oxygen sensor. The
in-line electrical connector and louvered end must
be kept free of grease, dirt or other contaminants.
Also, avoid using cleaning solvents of any type.
Do
not drop or roughly handle the oxygen sensor.
EXHAUST CROSSOVER PIPE
Figure C1-12 0, Sensor
Remove or Disconnect
The oxygen sensor may be difficult to remove
when engine temperature is below 48°C (120°F).
Excessive force may damage threads in exhaust
manifold or exhaust pipe.
~
1. Negative battery cable.
2. Electrical connector.
The vehicle should be raised on hoist because the
0, sensor is mounted behind the exhaust Y-pipe.
3. Carefully
back out Oxygen Sensor.
Install or Connect 1 i
Important I I
A special anti-seize compound is used on the
oxygen sensor threads. The compound consists
of a
liquid graphite and glass beads. The graphite will
burn away, but the glass beads will remain, making
the sensor easier to remove.
New or service sensors will already have the
compound applied to the threads. If a sensor is
removed from an engine, and, if for any reason it is to
be reinstalled, the threads must have anti-seize
compound applied before reinstallation.
1. Coat threads of oxygen sensor with anti-seize
compound
PIN 5613695 or equivalent if necessary.
2. Sensor, and torque to 41 N-m (30 ft. Ibs.).
3. Electrical connector.
4. Negative battery cable.
Throttle Position Sensor (TPS)
a Remove or Disconnect
1 Electrical connector.
2. Two 'I'PS attaching screws and retainers.
3. Sensor.

DRIVEABILITY AND EMISSIONS 2.8b (VIN 5) 6E3-C2-1
SECTION C2
FUEL CONTROL SYSEEIVI
CONTENTS
GENERAL DESCRIPTION . . . . . . . . . . . . . . . . C2-1 FUEL RAIL SERVICE . . . . . . . . . . . . . , . . . C2-6
PURPOSE ......................... C2-1 UNIT SERVICE PROCEDURES . . . . . . . . . . . C2-6
MODES OF OPERATION . . . . . . . . . . . . . . C2-1 COLD START TUBE & VALVE ASSEMBLY.. . C2-7
Starting Mode . . . . . . . . . . . . . . . . . . . C2-2 FUEL PRESSURE CONNECTION ASSEMBLY . C2-7
Clear Flood Mode . . . . . . . . . . . . . . . . . C2-2 FUEL BLOCK AND SEAL.. . . . . . . . . . . . . . C2-9
Run Mode .. .. . . . . . . . . . . . . . . . . . . C2-2 FUELINJECTORS .. . . . .. ... .... . . . ... C2-9
Acceleration Mode. . . . . . . . . . . . . . . . C2-2 Port Injectors wl Injector Retaining Clips C2-9
Deceleration Mode . . . . . . . . . . . . . . . C2-2 Fuel Pressure Regulator . . . . . . . . . . . . C2-10
Battery Voltage Correction Mode . . . . . C2-2 PORT INJECTORS . . . . . . . . . . . . . . . . . . . C2-10
Fuel Cutoff Mode . . . . . . . . . . . . . . . . . C2-3 PRESSURE REGULATOR.. . . . . . . . . . . . . . C2-10
Fuel Control System Components . . . . . C2-3 COLD START FUEL INJECTION SWITCH . . . C2-1 I
Basic System Operation. . . . . . . . . . . . . C2-3 THROTTLE BODY . . . . . . . . . . . . . . . . . . . C2-11
THROTTLE BODY UNIT . . . . . . . . . . . . . . . C2-3 THROTTLE BODY SERVICE IDENTIFICATION C2-11
FUEL RAIL.. . . . . . . . . . . . . . . . . . . . . . . . C2-3 MINIMUM IDLE SPEED ADJUSTMENT . . . . C2-14
FUEL INJECTOR.. . . . . . . . . . . . . . . . . . . . C2-3 UNIT REPAIR PROCEDURES . . . . . . . . . . . . C2-14
PRESSURE REGULATOR.. . . . . . . . . . . . . . C2-3 IDLE AIR CONTROL VALVE
IDLE AIR CONTROL (IAC) VALVE
. . . . . . . . C2-4 ASSEMBLY &GASKET.. . . . . . . . . . . . . . . C2-14
FUEL PUMP ELECTRICAL CIRCUIT . . . . . . . C2-4 IDLE AIRIVACUUM SIGNAL
DIAGNOSIS . . . . . . . . . . . . . . . . . . . . . . . . . C2-5 HOUSING ASSEMBLY . . . . . . . . . . . . . . . . C2-15
FUEL CONTROL SYSTEM . . . . . . . . . . . . . . C2-5 COOLANT CAVITY COVER & O-RING . . . . * C2-15
IDLE AIR CONTROL VALVE . . . . . . . . . . . . C2-5 IDLE AIR CONTROL / COOLANT
ON-CAR SERVICE . . . . . . . . . . . . . . . . . . . . . C2-5 COVERASSEMBLY .............,.... C2-16
PORT FUEL INJECTION COMPONENTS . . . . C2-5 FUEL PUMP RELAY . . . . . . . . . . . . . . . . . . C2-17
FUEL PRESSURE RELIEF PROCEDURE . . . . . C2-5 OIL PRESSURE SWITCH . . . . . . . . . . . . . . . C2-17
Plenum ........................ C2-5 PARTS INFORMATION . . . . . . . . . . . . . . . . . C2-17
Fuel Rail & Pressure Regulator Assembly . C2-5
GENERAL DESCRIPTION
PURPOSE
The basic function of the fuel control system is to
control fuel delivery to the engine.
Fuel is delivered to the engine by individual fuel
injectors mounted in the intake manifold near each
cylinder. The main control sensor is the oxygen
(02) sensor,
which is located in the exhaust manifold. The
O2
sensor tells the ECM how much oxygen is in the
exhaust gas, and the ECM changes the airlfuel ratio to
the engine by controlling the fuel injectors. The best
mixture to minimize exhaust emissions is
14.7 to 1,
which allows the catalytic converter to operate the
most efficiently. Because of the constant measuring
and adjusting of the airlfuel ratio, the fuel injection
system is called
a "Closed LoopJ' system (shown in
Figure C2-1).
ELECTRONIC CONTROL MODULE (ECM)
FUEL INJECTORS
EXHAUST OXYGEN
02 SENSOR
1 CATALYTIC CONVERTER
45 0997-6E
Figure C2-1 Closed Loop System
MODES OF OPERATION
The ECM looks at voltages from several sensors to
determine how much fuel to give the engine.
The fuel
is delivered under one of several conditions,
called
"modes". All the modes are controlled by the E:CM.
and are described below.

Starting Mode
When the ignition is first turned "ON," the ECM
will turn "ON" the fuel pump relay for two seconds,
and the fuel pump will build up pressure. The ECM
then checks the coolant temperature sensor, throttle
position sensor, and determines the proper airlfuel
ratio for starting. This ranges from 1.5
: 1 at -36°C (-
33°F ) to 14.7 : 1 at 94°C ( 201°F ). The ECM controls
the amount of fuel delivered in the STARTING mode
by changing how long the injectors are pulsed "ON".
The cold start valve (Figure C2-2) not controlled
by the ECM is used to provide additional fuel during
the starting mode to improve cold start-ups. This
circuit is important when the engine coolant
temperature is very low because the other injectors
would not be pulsed "ON" long enough to provide the
needed amount of fuel to start. The cold start valve is
somewhat different from the other injectors in that it
causes the fuel to be vaporized for a better combustible
mixture.
101 TUBE AND BODY ASSEMBLY
102 O-RING SEAL
- VALVE
103 O-RING SEAL
- BODY
104 O-RING SEAL
- TUBE
Figure C2-2 Cold Start Valve
The circuit is activated only in the crank mode.
The power is supplied directly from the starter
solenoid and is protected by the crank fuse. The
system is controlled by
a cold start fuel injection
switch which provides
a ground path for the valve
during cranking whenever engine coolant is below 35"
C (95°F).
Clear Flood Mode
If the engine floods, clear it by pushing the
accelerator pedal down all the way. The
ECM then
will turn "OFF" the fuel to the injectors. The
ECM
holds this injector rate as long as the throttle stays
wide open, and the engine rpm is below
600. If the
throttle position becomes less than
80%, the ECM
returns to the STARTING mode.
Run Mode
The RUN mode has two conditions called "Open
Loop" and "Closed Loop".
When the engine is first started, and rpm is above
400 rpm, the system goes into "Open Loop" operation.
In "Open Loop," the ECM will ignore the signal from
the oxygen
(02) sensor, and calculate the airlfuel ratio
based on inputs
from the coolant and MAF sensors.
The system will stay in "Open Loop" until the
following conditions are met:
1. The
O2 sensor has varying voltage output,
showing that it is hot enough to operate properly.
(This depends on temperature.)
2. The coolant sensor is above a specified
temperature about 25°C
(77°F).
3. A specific amount of time has elapsed after
starting the engine.
The specific values for the above conditions vary
with different engines, and are stored in the PROM or
Mem-Cal. When these conditions are met, the system
goes into "Closed Loop" operation. In "Closed Loop",
the ECM will calculate the airlfuel ratio (injector on-
time) based on the signal from the
O2 sensor. This
allows the airlfuel ratio to stay very close to 14.7: 1.
Acceleration Mode
The ECM looks at rapid changes in throttle
position and air flow, and provides extra fuel.
Deceleration Mode
The ECM looks at changes in throttle position and
air flow to reduce the amount of fuel. When
deceleration is very fast, the ECM can cut off fuel
completely for short periods.
The cold start fuel injection switch contains a
bimetal switch which opens the circuit at specified
Battery Voltage Correction Mode
coolant temperature. This bimetal is also heated by
the winding in the switch which would allow the valve When battery
voltage is low, the ECM can
to stay "ON" 8 seconds at -20°C or below. The time compensate
for the weak spark delivered by the
the switch stays closed varies inversely with coolant distributor
by:
temperature. In other words, as the coolant
@ Increasing the amount of fuel delivered;
temperature goes up the maximum cold start valve
@ Increasing the idle rpm; and
"ON" time goes down. Increasing ignition
dwell time.

DRIVEABILITY AND EMISSIONS 2.8L (VIN 5) 6E3-CZ-3
Fuel Cutofl Mode
No fuel is delivered by the injector when the
ignition is "OFF". This prevents dieseling. Also, fuel
is not delivered if no reference pulses are seen from
the distributor, which means the engine is not
running. This prevents flooding.
Fares Control System Components
The fuel control system is made up of the following
parts:
e Fuel Injectors
@ Throttle Body
e Fuel pump relay
@ Fuel Pressure Regulator
@ Fuel Rail
Basic System Operation
The fuel system (Figure C2-3) starts with the fuel
in the fuel tank. An electric fuel pump, located in the
fuel tank with the gage sending unit, pumps fuel to
the fuel rail through an in-line fuel filter. The pump is
designed to provide fuel at a pressure above the
pressure needed by the injectors. A pressure regulator
in the fuel rail keeps fuel available to the injectors at a
constant pressure. Unused fuel is returned to the fuel
tank by a separate line. For further information on
the fuel tank, in-line filter
, and fuel lines , see Section
"6C".
The injectors, are controlled by the ECM. They
deliver fuel in one of several modes, as described
above. In order to properly control the fuel supply, the
fuel pump is operated by the ECM thru the fuel pump
relay and oil pressure switch (see
"Fuel Pump
Electrical Circuit", Code 54).
THROTTLE BODY UNIT
The throttle body has a throttle valve to control
the amount of air delivered to the engine. The TPS
and
IAC valve are also mounted on the throttle body.
The throttle body contains vacuum ports located
at, above, or below the
throttIe valve. These ports
generate the vacuum signals needed by various
components.
FUEL RAIL
The fuel rail is mounted to the top of the engine.
It distributes fuel to the individual injectors. Fuel is
delivered to the input end of the rail by the fuel lines,
goes thru the rail, then to the pressure regulator.
Remaining fuel is then returned to the fuel tank.
Figure C2-3 Fuel System
FUEL INJECTOR
The fuel injector is a solenoid operated device
controlled by the ECM (See Figure C2-4). The ECM
turns
"ON" the solenoid, which opens a valve to allow
fuel delivery. The fuel, under pressure, is injected in a
conical spray pattern at the opening of the intake
valve. The fuel which is not used by the injectors
passes through the pressure regulator before being
returned to the fuel tank.
An injector which is stuck partly open will cause
loss of pressure after engine shut down, so long crank
times would be noticed on some engines. Also,
dieseling could occur because some fuel could be
delivered to the engine after the ignition is turned
"OFF".
PRESSURE REGULATOR
The pressure regulator is a diaphragm-operated
relief valve with injector pressure on one side and
manifold pressure on the other. The function of the
regulator is to maintain a constant pressure at the
injector at all times. The pressure regulator
compensates for engine load, by increasing fuel
pressure when it sees low engine vacuum.

6E3-CZ-4 Z.8L (WIN 5) DRIVEABILITY AND EMISSIONS
FUEL INJECTOR
1 INTAKE MANIFOLD
1 INTAKE VALVE
1 ELECTRICAL TERMINAL
151 "0" RING
1 FUEL RAIL 4.5 101ME
Figure C2-4 Fuel Injector
The pressure regulator is mounted on the fuel rail,
and is replaced as an assembly.
If the pressure is too low, poor performance could
result. If the pressure is too high, excessive odor and a
Code
45 may result. CHART A-7 has information on
diagnosing fuel pressure conditions.
IDLE AIR CONTROL (IAC) VALVE
The purpose of the idle air control (IAC) valve
(shown in Figure C2-5), is to control engine idle speed,
while preventing stalls due to changes in engine load.
The IAC valve, mounted in the throttle body,
controls bypass air around the throttle valve. By
moving a conical valve IN
(to decrease air flow) or
OUT (to increase air flow), a controlled amount of air
can move around the throttle plate. If rprn is too low,
more air is bypassed around the throttle valve to
increase rpm. If rprn is too high, less air is bypassed
around the throttle valve to decrease rpm.
The IAC valve moves in small steps called
"counts," which can be measured by some test
equipment which plugs into the ALDL.
During idle, the proper position of the IAC valve is
calculated by the ECM based on battery voltage,
coolant temperature, engine load, and engine rpm.
If
the rprn drops below a specified rpm, and the throttle
plate is closed, the ECM senses a near stall condition.
SINGLE TAPER VALVE
DUAL TAPER VALVE
BLUNT
PINTLE
Figure C2-5 IAC Valve Designs
The ECM will then calculate a new valve position to
prevent stalls.
If the IAC valve is disconnected and reconnected
with the engine running, the idle rprn may be wrong.
In this case, the IAC can be reset by starting the
engine momentarily and then turning the ignition
"OFF".
Different designs are used for the IAC valve. Re
sure to use the correct design when replacement is
required.
The IAC valve affects only the idle characteristics
of the vehicle. If it is open fully, too much air will be
allowed into the manifold and idle speed will be high.
If it is stuck closed, too little air will be allowed in the
manifold, and idle speed will be too low. If it is stuck
part way open, the idle may be rough, and will not
respond to engine load changes.
FUEL PUMP ELECTRICAL CIRCUIT
When the ignition is first turned "ON" without
the engine running, the ECM will turn the fuel pump
relay
"ON" for two seconds. This builds up the fuel
pressure quickly. If the engine is not started within
two seconds, the ECM will shut the fuel pump
"OFF"
and wait until the engine starts. As soon as the
engine is cranked, the ECM will turn the relay
"ON"
and run the fuel pump.

DRIVEABILITY AND EMISSIONS 2.8L (VIN 5) 6E3-C2-5
As a backup system to the fuel pump relay, the
fuel pump can also be turned "ON" by the oil pressure
switch. The oil pressure switch is a normally open
switch which closes when oil pressure reaches about
28
kPa (4 psi). If the fuel pump relay fails, the oil
pressure switch will close and run the fuel pump.
An inoperative fuel pump relay can result in long
cranking times, particularly if the engine is cold.
An inoperative fuel pump would cause a no start
condition. A fuel pump which does not provide enough
pressure can result in poor performance.
FUEL CONTROL SYSTEM
Some failures of this system will result in an
"Engine Cranks But Won't Run". If
this condition
exists, see CHART A-3. This chart will determine if
the problem is caused by the ignition system, ECM or
fuel pump circuit. If
it's determined to be a fuel
problem, CHART
A-7 will be used. This includes the
injectors, pressure regulator, fuel pump and fuel pump
relay. The fuel system wiring schematic is covered on
the facing page of Code CHART
54.
If a malfunction occurs in the fuel control system
it usually results in either a rich or a lean exhaust
condition. This condition is sensed by the oxygen
sensor and the ECM will change the fuel calculation
(injector pulse width) based on the
02 sensor reading.
The change made to the fuel calculation will be
indicated by a change in the block learn values which
can be monitored by a "Scan" tool. The normal block
learn values are around 128 and if the
O2 sensor is
sensing a lean condition, the ECM will add fuel and
this will result in a block learn value above 128. If the
02 sensor is sensing a rich exhaust the ECM will
reduce fuel to the engine and this will result in block
learn values below 128. Some variations in block
learn values are normal because all engines are not
exactly the same. However, if the block learn values
are
+ 10 counts from 128, a system problem exists. If
the block learn values are greater than 138, see Code
44 for items which can cause a lean system.
If the block learn values are less than 118, see
Code
45 for items which can cause the system to run
rich. If a driveability symptom exists, refer to the
particular symptom in Section
"B" for additional
items to check.
IDLE AIR CONTROL VALVE
A "Scan" tool will read IAC position in steps
(counts).
"0" steps indicates the ECM is commanding
the IAC to be driven all the way in, to a fully seated
position, and this is usually caused by a vacuum leak.
The higher the number of counts the more air being
allowed to pass the IAC valve. CHART C-2C can be
used to diagnosis the IAC valve. Also refer to "Rough, Unstable,
or Incorrect Idle, Stalling" in "Symptoms,"
Section
"B" for other possibilities for the cause of idle
problems.
ON-CAR SERVICE
PORT FUEL INJECTION COMPONENTS
CAUTION:
Before servicing an injector, fuel
rail, or pressure regulator, it is
necessary to relieve the pressure in
the fuel system, to minimize the risk
of fire and personal injury. (See
"Fuel Pressure Relief Procedure"
below). To reduce the chance of
personal injury, cover the fuel line
with a shop cloth to collect the fuel,
and then place the cloth in an
approved container.
FUEL PRESSURE RELIEF PROCEDURE
Connect fuel gage J 34730-1 or equivalent to fuel
pressure valve. Wrap a shop towel around fitting
while connecting gage to avoid spillage.
Install bleed hose into an approved container and
open valve to bleed system pressure.
Plenum
Remove or Disconnect
1. Negative battery cable.
2. Air
inlet duct at throttle body.
3. Throttle body retaining bolts
(2).
4. EGR pipe bolts (2).
5. Throttle cable bracket.
6. Plenum bolts (8).
Install or Connect
I. Plenum and gaskets.
2. Plenum bolts. See Figure C2-6.
3. Throttle cable bracket.
4. EGR pipe bolts.
5. Throttle body and bolts.
6. Air inlet duct
7. Negative battery cable.
Fuel Rail and Pressure Regulator Assembly
Important
When servicing the fuel rail assembly,
precautions must be taken to prevent dirt and
other contaminants from entering the fuel
passages. It is recommended that fittings
he
capped and holes be plugged during servicing.