1988 PONTIAC FIERO fuel pump

6E3-A-54 5.OL (VIN F) & 5.7L (VIN 8) DRIVEABILITY AND EMISSIONS
OXYGEN ( O2 ) SENSOR
CODE 44
OXYGEN SENSOR CIRCUIT
(LEAN EXHAUST INDICATED)
5.OL (VIN F) & 5.7L (VIN 8) '"F" "SERIES (PORT)
Circuit Description:
The ECM supplies a voltage of about .45 volt between terminals "D6" and "D7". (If measured with a 10
megohm digital voltmeter, this may read as low as .32 volts.) The
02 sensor varies the voltage within a range
of about 1 volt if the exhaust is rich, down through about .10 volt if exhaust is lean.
The sensor is like an open circuit and produces no voltage when it is below about 360°C
(600°F). An open
sensor circuit or cold sensor causes "Open Loop" operation.
Test Description: Numbers below refer to circled @
numbers on the diagnostic chart.
1. Code 44 is set when the O2 sensor signal voltage @
on CKT 412.
@ Remains below .2 volt for 50 seconds.
@ And the system is operating in "Closed Loop".
@
Diagnostic Aids:
Using the "Scan", observe the block learn values at
different rpm and air flow conditions. The "Scan" also
displays the block cells, so the block learn values can
@
be checked in each of the cells to determine when the
Code 44 may have been set.
If the conditions for Code
44 exist, the block learn values will be around 150.
@ - 02 sensor wire. Sensor pigtail may be @
m~spositioned and contacting the exhaust
manifold.
@ Check for intermittent ground in wire between
connector and sensor.
@ MAF Sensor. A mass air flow (MAF) sensor @
output that causes the ECM to sense a lower than
normal air flow will cause the system to go lean.
Disconnect the
MAF sensor and, if the lean
condition is gone, replace the
MAF sensor. Lean
Iniector(s). Perform
injector balance test
CHART C-2A.
Fuel Contamination. Water,
even in small
amounts, near the in-tank fuel pump inlet can be
delivered to the injectors. The water causes a lean
exhaust and can set a Code 44.
Fuel Pressure. System will be lean if pressure is
too low.
It may be necessary to monitor fuel
pressure while driving the car at various road
speeds
and/or loads to confirm. See Fuel System
diagnosis CHART
A-7.
Exhaust Leaks. If there is an exhaust leak,
outside air can be pulled into the exhaust and past
the sensor. Vacuum or crankcase leaks can cause
a lean condition.
AIR System. Be sure air is not being directed to
the exhaust ports while in "Closed Loop". If the
block learn value goes down while squeezing air
hose to left side exhaust ports, refer to CHART
C-
6.
If the above are
OK, it is a faulty oxygen sensor.

6E3-A-60 .5.0L (VIN F) & 5.7L (VIN 8) DRIVEABILITY AND EMISSIONS
340 - ORN
BULKHEAD CONN.
RELAY DRIVE
CODE 54
FUEL PUMP CIRCUIT
(LOW VOLTAGE)
5.OL (VIN F) & 5.7L (VIIN 8) "F" WRIES (PORT)
Circuit Description:
The status of the fuel pump CKT 120 (PPSW) is monitored by the ECM at terminal "H2" and is used to
compensate fuel delivery based on system voltage. This signal is also used to store a trouble code if the fuel
pump relay is defective or fuel pump voltage is lost while the engine is running. There should be about 12 volts
on CKT
120 for 2 seconds after the ignition is turned "ON", or any time references pulses are being received by
the ECM.
Code
54 will set, if the voltage at terminal "R2" is less than 2 volts for 1.5 seconds since the last reference
pulse was received. This code is designed to detect a faulty relay, causing extended crank time, and the code
will help the diagnosis of an engine that
"CRANKS BUT WILL NOT RUN".
If a fault is detected during start-up, the "Service Engine Soon" light will stay "ON" until the ignition is
cycled "OFF". However, if the voltage is detected below
2 volts, with the engine running, the light will only
remain "ON" while the condition exists.

DRIVEABILITY AND EMISSIONS 5.OL (VIN F) & 5.7L (VIN 8) 6E3-A-61
ONNECT FUEL PUMP
E LIGHT WITHIN 2
@ OIL PRESSURE NORMAL.

DRIVEABILITY AND EMISSIONS 5.OL (VIN F) & 5.7L (VIN 8) 6E3-8-3
@ A faulty in-tank fuel pump check valve will @
allow the fuel in the lines to drain back to the
tank after the engine is stopped. To check for
this condition:
e
Perform Fuel System Diagnosis, CHART A-7.
@ Remove spark plugs. Check for wet plugs,
cracks, wear, improper gap, burned electrodes,
@
or heavy deposits. Repair or replace as
necessary. If
engine starts but then immediately stalls
open distributor by-pass line. If engine then
starts and runs OK, replace pickup coil.
If engine starts and stalls disconnect MAF
sensor. If engine then
r~lns and sensor
connections are OK, replace
thr. )t.ft+rl'.
Basic engine problem.
HESITATION, SAG, STUMBLE
Definition: Momentary lack of response as the accelerator i., pl,ihcc! dowt-
Can occur at all car speeds. Usually most severe when first tryine, lo m,tlir. LII~.
car move, as from a stop sign. May cause the engine to sta!! 1, e er., riu~~~!~
s Perform careful visual check as described at
start of Section
"B".
@ CHECK:
- Fuel pressure. See CHART A-7. Also, check
for water contaminated fuel.
- Air leaks at air duct between MAF sensor and
throttle body.
- Spark plugs for being fouled or faulty wiring.
- Mem-Cal number. Also check service bulletins
for latest Mem-Cal.
- TPS for binding or sticking. Voltage should
increase at
a steady rate as throttle is moved
toward WOT.
- Ignition timing. See emission control
information label.
- Generator output voltage. Repair if less than 9
or more than 16 volts.
- HE1 ground, CKT 453.
- Canister purge system for proper operation.
See CHART C-3.
- EGR - See CHART C-7.
e Perform injector balance test CHART C-2A.
SURGES AND/OR CHUGGLE
Definition: Engine power variation under steady
throttle or cruise. Feels like the car speeds up and
slows down with no change in the accelerator pedal.
@ Be sure driver understands transmission
converter clutch and
AJC compressor operation
in owner's manual.
Perform careful visual inspection as described
at start of Section
"B".
e CHECK:
- Loose or leaking air duct between MAF sensor
and throttle body.
- Generator output voltage. Repair if less than 9
or more than 16 volts.
- EGR - There should be no EGR at idle. See
CHART C-7.
- Vacuum lines for kinks or leaks.
- Ignition timing. See emission control
information label.
- In-line fuel filter. Replace if dirty or plugged.
- Fuel pressure while condition exists. See
CHART A-7.
@ Inspect oxygen sensor for silicon contamination
from fuel, or use of improper RTV sealant. The
sensor may have a white, powdery coating and
result in a high but false signal voltage (rich
exhaust indication). The ECM will then reduce
the amount of fuel delivered to the engine,
causing a severe driveability problem.
@ Remove spark plugs. Check for cracks, wear,
improper gap, burned electrodes, or heavy
deposits. Also check condition of distributor
cap, rotor, and spark plug wires.
@ 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 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
1181, refer to "Diagnostic Aids" on facing page
of Code
45.

6E3-B-4 5.OL (VIN F) & 5.7L (VIN 8) 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
start of Section "B".
@ Compare customer's car to similar unit.
Make sure the customer's car has an actual
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.
- EGR operation for being open, or partly open
all the time
- CHART C-7.
- Exhaust system for possible restriction: See
CHART
B-1.
- Inspect exhaust system for damaged or
collapsed pipes.
- Inspect muffler for heat distress or possible
internal failure.
- For possible plugged catalytic convertor by
comparing exhaust system backpressure on
each side at engine. Check backpressure by
removing
A.1.R check valves near exhaust
manifolds. See CHART
B-1 for procedure.
- 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.
- Check for excessive knock retard. See CHART
C-5.
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.
- 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.
@ Checkforpoorfuelquality.
@ Remove carbon with top engine cleaner. Follow
instructions on can.
@ Check ESC system
See CHART C-5
@ 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
1181, refer to "Diagnostic Aids" on facing page of
Code 45.

DRIVEABILITY AND EMISSIONS 5.OL (VIN F) & 5.7L (VIN 8) 6E3-C2-1
SECTION C2
FUEL CONTROL SYSEENI
CONTENTS
GENERAL DESCRIPTION . . . . . . . . . . . . . . . . C2-1
PURPOSE ........................ C2-1
MODES OF OPERATION . . . . . . . . . . . . . . C2-2
Starting Mode . . . . . . . . . . . . . . . . . . . C2-2
Clear Flood Mode.. . . . . . . . . . . . . . . . C2-2
Run Mode.. . . . . . . . . . . . . . . . . . . . . . C2-2
Acceleration Mode.. . . . . . . . . . . . . . . C2-2
Deceleration Mode . . . . . . . . . . . . . . . C2-3
Battery Voltage Correction Mode . . . . . C2-3
Fuel Cutoff Mode . , . . . . . . . . . . . . . . . C2-3
FUEL CONTROL SYSTEM . . . . . . . . . . . . . . C2-3
Basic System Operation . . . . . . . . . . . . C2-3
Throttle Body Unit . . . . . . . . . . . . . . . . C2-3
Fuel Rail . . . . . . . . . . . . . . . . . . . . . . . C2-3
Fuel Injectors . . . . . . . . . . . . . . . . . . . . C2-3
Pressure Regulator . . . . . . . . . . . . . . . C2-4
IAC Valve . . . . . . . . . . . . . . . . . . . . . . . C2-4
Fuel Pump Electrical Circuit . . . . . . . . , C2-5
DIAGNOSIS
......................... C2-5
FUEL CONTROL SYSTEM . . . . . . . . . . . . . . C2-5
IDLE AIR CONTROL VALVE . . . .. 0.. . a. C2-5
FUEL SYSTEM PRESSURE TEST . .. . . . . . . C2-5
ON-CAR SERVICE
. . . . . . . . . . . . . . . . . . . . . C2-5
PORT FUEL INJECTION COMPONENTS . . . . C2-5
FUEL PRESSURE RELIEF PROCEDURE . . . . . C2-5
Plenum ........................ C2-5
FUEL RAlL ASSEMBLY . . . . . . . . . . . . . . . . C2-6
FUEL
RAlL SERVICE . . . . . . . . . . . . . . . . . . . C2-7
IDENTIFICATION . . . . . . . . . . . . . . . . . . . C2-7
UNlT SERVICE PROCEDURES .. . . . . . . . .. C2-7
COLD START TUBE & VALVE ASSEMBLY.. . C2-7
PARTS INFORMATION
. . . . . . . . . . . . . . . C2-9
FUEL PRESSURE CONNECTION ASSY. . . . . C2-10
FUEL INJECTORS (Rail Removed) . . . . . . . . C2-10
PRESSURE REGULATOR (Rail Removed) . . . C2-10
COLD START FUEL INJECTION SWITCH . . . C2-11
THROTTLEBODY ................... C2-11
THROTTLE BODY SERVICE IDENTIFICATION
. C2-12
UNlT REPAIR PROCEDURES . . . . . . . . . . . . C2-12
TPS Adjustment .............. C2-12
MINIMUM IDLE SPEED CHECK . . . . . . . . . . . C2-12
PARTSINFORMATION ................. C2-15
IDLE AIR C'NT' L VALVE ASSY & GASKET . . C2-15
CLEAN AIR COVER &GASKET . . . . . . . . . . C2-15
IDLE AIR CONTROUCOOLANT CVR. ASSY . C2-15
Throttle Body Removed From Engine . . C2-15
FUEL PUMP RELAY . . . . . . . . . . . . . .,. . . . C2-16
OIL PRESSURE SWITCH . . . . . . . . . . . . . . . C2-16
PARTS INFORMATION . . . . . . . . . . . . . . . . . C2-16
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 electronic control module (ECM) how
much oxygen is in the exhaust gas.
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
Loop" system (shown in Figure
C2-I).
EXHAUST OXYGEN 02 SENSOR
CATALYTIC CONVERTER
Figure C2-1 "Closed Loop" System

6E3-C2-2 5.OL (VIN F) & 5.7L(VIN 8) DRIVEABILITY AND EMISSIONS
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 ECM
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:l 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.
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).
100 VALVE - COLD START
101 TUBE AND BODY ASSEMBLY
102 O-RING SEAL
- VALVE
103 O-RING SEAL
- BODY
104 O-RING SEAL -TUBE
The cold start fuel injection switch contains a
bimetal switch which opens the circuit at specified
coolant temperature. This bimetal is also heated
by
the winding in the switch, which would allow the
valve to stay "ON" 8 seconds at
-20" C or below. The
time the switch stays closed varies inversely with
coolant temperature. In other words, as the coolant
temperature goes up the maximum cold start valve
"ON" time goes down.
Clear Flood Mode
If the engine floods, clear it by pushing the
accelerator pedal down all the way. The ECM then
pulses the injectors at an airlfuel ratio of
20:l. 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
(Oz) 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 40°C
(104°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 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 various sensors but
mainly
the O2 sensor. This allows the air 1 fuel 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.
Figure C2-2 Cold Start Valve

DRIVEABILITY AND EMISSIONS 5.OL (VIN F) & 5.7L (VIN 8) 6E3-CZ-3
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 may shut off fuel
completely for short periods.
Battery Voltage Correction Mode
When battery voltage is low, the ECM can
compensate for the weak spark delivered by the
distributor by:
@ Increasing the amount of fuel delivered;
@ Increasing the idle rpm; and
@ Increasing ignition dwell time.
Fuel Cutoff 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.
FUEL CONTROL SYSTEM
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, depending on manifold 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 through 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 the IAC valve are also mounted on the throttle
body. The throttle body contains vacuum ports located
at, above, or below the
throttIe valve. 'I'hese ports
generate the vacuum signals
needed I,y v~irious
Figure C2-3 Fuel System
components. Engine coolant is directed through the
coolant cavity, on the bottom of the throttle body, to
warm the throttle valve and prevent icing.
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 through the rail, then to the pressure regulator.
Remaining fuel is then returned to the fuel tank.
Fuel Injectors
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".