1988 PONTIAC FIERO distributor

6E3-A-22 5.OL (VIN F) & 5.7L (VIN 8) DRIVEABILITY AND EMISSIONS
COLD START SWITCH
CONNECTOR
CLOSED BELOW
3S°C.
8 SEC. TIME LIMIT
COOLANT
CHART A99
COLD START VALVE CIRCUIT TEST
5.OL (VIN F) & 5.7L (VIN 8) "F" SERIES (PORT)
Circuit Description:
The cold start valve is used to provide additional fuel cluring the crank mode to improve cold start-ups. This
circuit is important when engine coolant temperature is low because the other injectors are not pulsed
"ON"
long enough to provide the needed amount of fuel to start.
The circuit is activated only in the crank mode. The power is supplied directly from the starter solenoid and
is protected by a fuse. The system is controlled by a cold start fuel injection switch which provides a ground path
for the valve during cranking when engine coolant is below 35°C (95°F).
The cold start fuel injection switch consists of a bimetal material which opens at a specified coolant
temperature. This bimetal is also heated by the winding in the thertnal switch which allows the valve lo stay
"ON" for 8 seconds at -20°C (-4°F) coolant. The time the switch will stay closed varies inversely with coolant
temperature. In other words, as the coolant temperature goes up, the cold start valve
"ON" time goes down.
Test Description: Numbers below refer to circled
numbers on the diagnostic chart.
1. Disconnecting the distributor 4-way connector
will disable the other injectors. The amount of
pressure drop depends on the temperature of the
engine. This test could also be performed
by
removing the two injector fuses.
2. This test will determine the continuity through
the switch to ground.

6E3-B-2 5.OL (VIN F) & 5.7L (VIN 8) DRIVEABILITY AND EMISSIONS
Problem may or may not turn "ON" the "Service Engine Soon" light, or store a code.
DO NOT use the Trouble Code Charts in
An intermittent "Service Engine Soon" light
Section A for intermittent problems. The fault must
with no stored code may be caused by:
be present to locate the problem. If a fault is
@ Ignition coil shorted to ground and arcing at
intermittent, use of Trouble Code Charts
may result
spark plug wires or plugs.
in replacement of good parts.
"Service Engine Soon" light wire to
ECM
@ Most intermittent problems are caused by
shorted to ground. (CKT 419).
faulty electrical connections or wiring. Perform
Diagnostic "Test" Terminal wire to ECM,
careful check as described at start of Section
shorted to
ground.(CKT 451)
"B". Check for:
@ ECM power grounds. See ECSI wiring
@ Poor mating of the connector halves, or diagrams.
terminals not fully seated in the connector
@ Loss of trouble code memory. To check,
body (backed out). disconnect TPS and idle engine until "Service
@ Improperly formed or damaged terminals.
Engine Soon" light comes on. Code 22 should be
All connector terminals in problem circuit
stored, and kept in memory when ignition is
should be carefully reformed or replaced to turned "OFF". If not, the ECM is faulty.
insure proper contact tension.
@ Check for an electrical system interference
@ Poor terminal to wire connection. This caused by a defective relay, ECM driven
requires removing the terminal from the
solenoid, or switch. They can cause a sharp
connector body to check. See "Introduction"
electrical surge. Normally, the problem will
to Section
"6E". occur when the faulty component is operated.
@ If a visual check does not find the cause of the @ Check for improper installation of electrical
problem, the car can be driven with a voltmeter
options, such as lights,
%way radios, etc.
connected to
a suspected circuit. A "Scan" tool
EST wires should be kept away from spark plug
can also be used for monitoring input signals to wires, distributor wires, distributor housing,
the ECM to help detect intermittent conditions. coil, and generator. Wire from
ECM to
An abnormal voltage, or "Scan" reading, when distributor
(CKT 453) should be a good
the problem occurs, indicates the problem
may connection.
be in that circuit. If the wiring and connectors
@ Check for open diode across AIC compressor
check OK and a Trouble Code was stored for a
clutch, and for other open diodes (see wiring
circuit having a sensor, except for Codes
43, 44, diagrams).
and 45, substitute a known good sensor and
recheck.
HARD START
Definition: Engine cranks OK, but does not start for a long
time. Does eventually run, or may start but immediately dies.
Perform careful check as described at start of
Section
"B".
@ Make sure driver is using correct starting
procedure.
@ CHECK:
- TPS for sticking or binding or a high TPS
voltage with the throttle closed (should read
less than
.700 volts).
- High resistance in coolant sensor circuit or
sensor itself. See Code 15 chart or with
a
"Scan" tool compare coolant temperature with
ambient temperature on a cold engine.
- Fuel pressure CHART A-7.
- Water contaminated fuel.
- EGR operation. Be sure valve seats properly and
is not staying open. See CHART C-7.
- Both injector fuses (visually inspect).
- Ignition system - Check distributor for:
Proper Output with ST-125.
Worn shaft.
Bare and shorted wires.
Pickup coil resistance and connections.
Loose ignition coil ground.
Moisture in distributor cap.
@ If problem exists in cold weather, check cold start
valve. See CHART A-9.

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.

DRIVEABILITY AND EMISSIONS S.OL (VIN F) & 5.7L (VIN 8) 6E3-B-5
Definition: Steady pulsation or jerking that follows engine
speed, usually more pronounced as engine load increases. The
exhaust has
a steady spitting sound at idle or low speed.
@ Perform careful visual check as described at blink
at any connector, it is a faulty injector drive
start of Section
"B". circuit harness, connector, or terminal.
@ Check for missing cylinder by: @ Perform the Injector Balance Test. See CHART
1. Disconnect IAC valve. Start engine. C-2A.
Remove one spark plug wire at a time
@ CHECK:
using insulated pliers. - Spark plug wires by connecting ohmmeter to
2. If there is an rpm drop on all cylinders ends
of each wire in question. If meter reads over
(equal to within
50 rpm), go to "ROUGH, 30,000
ohms, replace wire(s).
UNSTABLE, OR INCORRECT IDLE, - Fuel System - Plugged fuel filter, water, low
STALLING" symptom. Reconnect IAC pressure. See CHART A-7.
valve.
- Valve timing.
3. If there is no rpm drop on one or more - Secondary voltage using a shop ocilliscope or a
cylinders, or excessive variation in drop, spark tester 5-26792 (ST-125)
or equivalent.
check for spark on the suspected
@ Visually inspect distributor cap and rotor for
cylinder(s) with J 26792 (ST-125) Spark moisture, dust, cracks, burns, etc. Spray cap and
Gap Tool or equivalent. If no spark, see plug wires with fine water mist to check for
Section 6D for Intermittent Operation or shorts.
Miss. If there is spark, remove spark
@ A miss condition can be caused by EM1
plug(s) in these cylinders and check for: (Electromagnetic Interference) on the reference
- Cracks circuit. EM1 can usually be detected by
- Wear monitoring engine rpm with a "Scan" tool. A
- Improper Gap sudden
increase in rpm with little change in
- Burned Electrodes actual engine rpm change, indicates EM1 is
- Heavy Deposits present.
@ Perform compression check on questionable If
the problem exists, check routing of secondary
cylinder(s) found above. If compression is low, wires, check
all distributor ground circuits.
repair as necessary. See Section
"6". @ Remove rocker covers. Check for bent pushrods,
@ Disconnect all injector harness connectors. worn
rocker arms, broken valve springs, worn
Connect
5-34730-2 Injector Test Light or camshaft
lobes. Repair as necessary. See Section
equivalent 6 volt test light between the
"6A".
harness terms, of each injector connector and
note light while cranking. If test light fails to
BACKFIRE
Definition: Fuel ignites in intake manifold, or
in exhaust system, making a loud popping noise.
@ CHECK: - Spark plugs for crossfire also inspect (distributor
- Loose wiring connector or air duct at MAF
cap, spark plug wires, and proper routing of plug
sensor. wires).
- Compression - Look for sticking or leaking - Ignition system for intermittent condition. (See
valves. Section
"6D").
- EGR operation for being open all the time. See - Engine timing - see emission control information
CHART C-7. label.
- EGR gasket for faulty or loose fit. - Perform fuel system diagnosis check, CHART A-
- Valve timing. 7A.
- Output voltage of ignition coil using a shop - Perform injector balance test CI-IART C-2A.
ocilliscope or spark tester 5-26792 (ST-125) or
- A.I.R. system check valves - See Section "C-6".
equivalent.

DRIVEABILITY AND EMISSIONS 5.0L (VIN F) & 5.7L (VIN 8) 6E3-C1-1
SECTION C1
ELECTRONlC CONTROL MODULE (ECM) AND SENSORS
CONTENTS
GENERAL DESCRIPTION ................ C1-I
ELECTRONIC CONTROL MODULE ....... C1-I
PJIEM-CAL......................... C1-I
ECM Function.. .................. C1-I
INFORMATION SENSORS ............. Cl-2
Engine Coolant Temperature Sensor . . C1-2
MAF Sensor ..................... C1-2
MAT Sensor .................... C1-2
Oxygen (02) Sensor. ............... C1-3
Throttle Position Sensor ............ C1-3
Knocksensor .................... C1-3
Vehicle Speed Sensor .............. C1-3
...... ParkINeutral Switch (Auto Only) C1-3
NC "ON" Signal .................. C1-4
Distributor Reference Signal ......... C1-4
DIAGNOSIS
......................... C1-4
ECM............................. C1-4
MEM-CAL......................... C1-4
ECMINPUTS....................... C1-4
........ Coolant Temperature Sensor C1-5
GENERAL DESCRIPTION
ELECTRONIC CONTROL MODULE (ECM)
The electronic control [nodule (ECM) (Figure C1-
11, located under the instrument panel, is the control
center of the fuel injection system. It constantly looks
at the information from various sensors,
and controls
the systems that affect vehicle performance. The
ECM performs the diagnostic function of the system.
-- Figure C1-1 - Electronic Control Module (ECM)
MAF Sensor ..................... C1-5
MAT Sensor ..................... C1-5
Oxygen (02) Sensor ............... C1-5
TPS ........................... C1-5
VSS ........................... C1-5
PIN Switch ...................... C1-5
NC Request Signal ................ C1-5
Reference Signal ................. C1-5
ON-CAR SERVICE
..................... C1-5
ELECTRONIC CONTROL MODULE ....... C1-5
ECM or MEM-CAL REPLACEMENT ....... C1-6
Funct~onal Check ................. C1-7
COOLANT SENSOR .................. C1-7
MAFSENSOR ...................... C1-8
MAF SENSOR POWER & BURN-OFF RELAY . C1-8
OXYGEN SENSOR .................. C1-8
THROTTLE POSITION SENSOR ......... C1-8
PARKINEUTRAL SWITCH ............. C1-9
PARTS INFORMATION
................. C1-9
It can recognize operational problems, alert the driver
through the "Service Engine Soon" light, and store a
code or codes which identify the problem areas to aid
the technician in making repairs. See Section
"6E"
for more information on using the diagnostic function
of the
ECM.
For service, this ECM only consists of two parts: a
controller (the ECM without a
Mem-Cal) and an
assembly called a Mem-Cal. (This stands for "Memory
and Calibration" Unit).
M EM-CAL
This assembly contains both thc functions of thc
PROM and CalPak. Like the PROM, it contains the
calibrations needed for a specific vehicle as well as the
back-up fuel control circuitry required if the rest of the
ECM becomes damaged or faulty.
ECM Function
The ECM supplies either 5 or 12 volts to power
various sensors or switches.
This is done through
resistances in the ECM which are so high in value
that a test light will not light when connected to the
circuit.
In some cases, even an ordinary shop
voltmeter will not give an accurate reading because
its resistance is too low. Therefore, a
10 nleg ohm
input impedance digital voltmeter is
requircd to
assure accurate voltage readings.

6E3-C1-4 5.0L (VIN F) & 5.7L(VIN 8) DRIVEABILITY AND EMISSIONS
See Section "8A" for more information on the PIN
switch, which is part of the neutrallstart and backup
light switch assembly.
NC "ON" Signal
This signal tells the ECM that the NC selector
switch is turned "ON", and that the pressure cycling
switch is closed. The
ECM uses this to adjust the idle
speed when the air conditioning is working.
[f this signal is not available to the ECM, idle may
be rough, especially when the NC compressor cycles.
The voltage at ECM terminal "B8" should equal
battery voltage on a
C60 system and about 5 volts on a
C68 option, when
NC is requested and the pressure
cycling switch is closed.
Distributor Reference Signal
The distributor sends a signal to the ECM to tell it
both engine rpm and crankshaft position. See ignition
system Section
"C4" for further information.
DIAGNOSIS
To read the codes, use a "Scan" tool or ground the
diagnostic terminal with the engine not running and
the ignition "ON". The "Service Engine Soon" light
will flash Code 12 three times and then flash each code
stored in memory three times. All codes stored in
memory would have been read when Code 12 was
flashed again. No new codes can be stored when in the
diagnostics mode (diagnostics lead grounded). This
eliminates confusion while the system is being worked
on.
To clear the codes from memory:
@ Ignition "OFF".
@ Disconnect battery pigtail, located near the
battery, for 30 seconds.
Since the ECM can have a failure which may
affect only one circuit, following the diagnostic
procedures in this section will determine which circuit
has a problem and where it is.
If a diagnostic chart indicates that the
ECM
connections or ECM is the cause of a problem,and the
ECM is replaced, but does not correct the problem, one
of the following may be the reason:
-
@ There is a problem with the ECM terminal
connections.
- The diagnostic chart will say ECM
connections or ECM. The terminals may have to
be removed from the connector in order to check
them properly.
@ The ECM, or Mem-Cal is not correct for the
application.
- The incorrect components may cause
a malfunction and
may or may not set u code.
@ The problem is intermittent. - 'l'his means that the
problem is not present at the time the system is
being checked. In
this case, refer to the "Symptoms" portion
of the
manual and make a careful physical inspection
of
all portions of the system involved.
@ Shorted solenoid, relay coil, or harness. - Solenoids
and relays are turned
"ON" and "OFF" by the
ECM, using internal electronic switches called
"Drivers".
A shorted solenoid, relay coil, or harness in a
GMP4 computer will not damage the ECM,
but will cause the circuit and controlled
component to be inoperative. When the
circuit fault is not present or has been
repaired, the
"Quad-Driver" will again
operate in a normal manner due to it's fault
protected design.
If a fault has been repaired
in a circuit controlled by a "Quad-Driver",
the original ECM should be reinstalled and
the circuit checked for proper operation.
ECM replacement will
not be necessary if the
repaired circuit or component now operates
correctly.
534636 or BT 8405 testers or equivalent provide a
fast, accurate means of checking for a shorted coil
or a short to battery voltage.
@ The Mem-Cal may be faulty. - Although these
rarely fail, it operates as part of the ECM.
Therefore, it could be the cause
of the problem.
Substitute a known good Mem-Cal.
@ The replacement ECM may be faulty - After the
ECM is replaced, the system should be rechecked
for proper operation. If the diagnostic chart again
indicates the ECM is the problem, substitute a
known good ECM. Although this is a rare
condition, it could happen.
ECM
A faulty ECM will be determined in the diagnostic
charts.
MEM-CAL
An incorrect or faulty Mem-Cal, which is part of
the ECM, may set a Code 41 or 52. Also, be sure Mem-
Cal is fully seated and latched in the socket.
ECM INPUTS
A11 of the sensors and input switches can be
diagnosed by the use of
a "Scan" tool. Following is a
short clescription of how the sensors and switches can
he diagnosed
by the use of a "Scan" tool. The "Scan"
can also be used to compare the values for a normal
running engine with the engine you're diagnosing.

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".

DRIVEABILITY AND EMISSIONS 5.OL (VIN F) & 5.7b (VIN 8) 6E3-CZ-13
IDLE STOP SCREW
ASSEMBLY

IDLE STOP
SCREW PLUG
Figure C2-16 Removing Idle Stop Srew Plug
60 IDLE AIR/VACUUM SIGNAL HOUSING
70 IDLE AIR CONTROL VALVE (IAC)
71 IAC GASKET
Figure C2-17 Idle Air Control Valve Assembly
3. With IAC motor connected, ground diagnostic
terminal. Measure
4. Turn "ON" ignition, do not start engine. Wait at @ Distance from gasket mounting surface of IAC
least 30 seconds. valve assembly
(70) to tip of pintle,
5. With ignition
"ON", disconnect IAC electrical (Dimension
"A" in Figure C2-17).
connector.
Important
6. Disconnect
the distributor set-timing connector.
7. Start
engine and allow to go "Closed Loop".
8. Remove
ground from diagnostic terminal.
9. Adjust idle stop screw to 400 rpm 5.01,, 450 rpm
5.7L in neutral for manual or automatic
transmission vehicles.
10. Turn ignition "OFF" and reconnect connector at
IAC motor.
11. Adjust TPS, if necessary:
@ With ignition "ON", use a "Scan" tool or 3
jumper wires and adjust TPS to obtain .54 volt
+ .08 volt. - @ Tighten screws, then recheck reading to
insure adjustment has not changed.
12. Start engine and inspect for proper idle operation.
IDLE AIR CONTROL VALVE ASSEMBLY AND
CASKET
ORemove or Disconnect
1. Electrical connector at idle air control valve
assembly (70).
2. IAC valve assembly from IACVIcoolant cover
assembly.
3. IAC valve assembly gasket (71) and discard.
NOTICE: Before installing new idle air control valve
assembly, the position of its
pinlle MUST
be checked. If pintle is extended too far,
damage to the assembly
may occur
Adjust
If distance is greater that 28 mm (1 118 in.), reduce
it as follows:
a. If IAC valve assembly has a "collar" around
electrical connector end, use firm hand pressure
on pintle to retract it. (A slight side-to-side motion
may help.)
b. If
IAC valve assembly has no "collar", compress
pintle-retaining spring toward body of IAC valve
and try to turn pintle clockwise.
@ If pintle will turn, continue turning until
28mm
(1 118 in.) is reached. Return spring to
original position, with straight part of spring
end lined up with flat surface under pintle
head.
@ If pintle will not turn, use firm hand pressure
to retract it.
Install or Connect
1. New IAC valve assembly gasket (71) on IAC valve
assembly
(70).
2. IAC valve assembly in IACVIcoolant cover
assembly (61).
Tighten
IAC valve assembly to 18N.m (13 ft. Ibs.), with
wrench on hex surface only.
3. Electrical connector at IAC valve assembly (70).