1988 PONTIAC FIERO ignition

&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.

DWI\/EABILITV AND EMISSIONS 2.8L (VIN 5) 6E3-B-5
CU"T SUP, MISSES
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
start of Section
"B".
@ Check for missing cylinder by:
1. Disconnect IAC valve. Start engine.
Remove one spark plug wire at a time
using insulated pliers.
2. If there is an rpm drop on all cylinders
(equal to within
50 rpm), go to "ROUGH,
UNSTABLE, OR INCORRECT IDLE,
STALLING" symptom. Reconnect IAC
valve.
3. If
there is no rprn drop on one or more
cylinders, or excessive variation in drop,
check for spark on the suspected
cylinder(s) with J 26792 (ST-125) Spark
Gap Tool or equivalent.
If no spark, see
Section
"6D" for intermittent operation or
miss. If there is spark, remove spark
plug(s) in these cylinders and check for:
- Cracks
- Wear
- Improper gap
- Burned electrodes
- Iieavy deposits
@ Perform compression check on questionable
cylinder(s) found above. If compression is low,
repair as necessary. See Section
"6".
@ Disconnect all injector harness connectors.
Connect
5-34730-2 injector test light or
equivalent 6 volt test light between the
harness terms, of each injector connector and
note light while cranking. If test light fails to blink
at any connector, it is a faulty injector drive
circuit harness, connector, or terminal.
@ Perform the injector balance test. See CHART C-
2A.
s CHECK:
- Spark plug wires by connecting ohmmeter to
ends of each wire in question. If meter reads over
30,000 ohms, replace wire(s1.
- Fuel System - Plugged fuel filter, water, low
pressure. See
CHART A-7.
- Valve timing.
- Secondary voltage using a shop ocilliscope or a
spark tester 5-26792 (ST-125) or equivalent.
@ Visually inspect distributor cap and rotor for
moisture, dust, cracks, burns, etc. Spray cap and
plug wires with, fine water mist to check for
shorts.
@ A miss condition can be caused by EM1
(Electromagnetic Interference) on the reference
circuit.
EM1 can usually be detected by
monitoring engine rpm with a "Scan" tool. A
sudden increase in rpm with little change in
actual engine rpm change, indicates
EM1 is
present. If the problem exists, check routing of secondary
wires, check all distributor ground circuits.
@ Remove rocker covers. Check for bent pushrods,
worn rocker arms, broken valve springs, worn
camshaft lobes. Repair as necessary. See Section
"6A".
BACKFIRE
Definition: Fuel ignites in intake manifold, or
in exhaust system, making a loud popping noise.
CHECK:
- Loose wiring connector or air duct at MAF
sensor.
- Compression - Look for sticking or leaking
valves.
- EGR operation for being open all the time. See
CHART C-7.
- EGR gasket for faulty or loose fit .
- Valve timing.
- Output voltage of ignition coil using a shop
ocilliscope or spark tester 5-26792 (ST-125) or
equivalent.
- Spark plugs for crossfire also inspect (distributor
cap, spark plug wires, and proper routing of plug
wires).
- Ignition system for intermittent condition. (See
Section
"6D").
- Engine timing - see Emission Control
Information label.
- Perform fuel system diagnosis check, CIIART A-
7A.
- Perform injector balance test, CHART C-2A.
- Deceleration valve (2.8L ~nanualltrans) - See
Section
"C6".
- A.I.R. system check valves - See Section "C-6".

6E3-B-6 2.8L (VIN 5) DRIVEABILITY AND EMISSIONS
POOR FUEL ECONOMY
Definition: Fuel economy, as measured by an actual road test, is
noticeably lower than expected. Also, economy is noticeably lower than
it was on this car at one time, as previously shown by an actual road test.
@ Perform careful visual check as described at
start of Section "B".
8 CHECK:
- Coolant level.
- Engine thermostat for faulty part (always
open) or for wrong heat range. See Section
"6B".
- Compression
- Ignition timing. See Emission Control
Information label.
- TCC for proper operation. A "ScanJ' should
indicate an rpm drop when the TCC is
commanded "ON". See CHART C-8.
- Induction system and crankcase for air leaks.
8 Check for exhaust restriction.
See CHART
B-1.
DIESELING, RUN-ON
Definition: Engine continues to run after key is
turned "OFF", but runs very roughly. If engine runs
smoothly, check ignition switch and adjustment.
8 Check injectors for leaking. See CHART A-7.
ROUGH, UNSTABLE, OR INCORRECT IDLE, STALLING
Definition: The engine runs unevenly at idle. If bad enough, the car may
shake. Also, the idle may vary in rpm (called "hunting"). Either
condition
may be bad enough to cause stalling. Engine idles at incorrect speed.
@ Perform careful visual check as described at
start of Section "B".
@ CHECK:
- Throttle linkage for sticking or binding. Also
check TPS adjustment. Refer to Section
"C2".
- Ignition timing. See Emission Control
Information label.
- ECM ground circuits.
- IAC system. See CHART C-2C.
- Generator output voltage. Repair if less than 9
or more than 16 volts.
- PIN switch circuit. See CHART C-lA, or use
"SCAN" tool.
- Injector balance. See CHART C-'LA.
- PCV valve for proper operation by placing
finger over inlet hole in valve end several times.
Valve should snap back. If not, replace valve.
- Evaporative Emission Control System. CHART
C-3.
- A/C signal to ECM terminal "B8" (5.OL & 5.7L).
"Scan" tool should indicate AIC is being
requested when ever
A/C is selected and the
pressure cycling switch is closed.
- A/C system operation (2.8L) - See CHAR'l' (2-10.
- Minimum idle speed. See Section "C2".
- Loose or damaged MAF sensor duct between
sensor and throttle body.
- Power Steering Pressure Switch (2.81, - See
CHART
C-1E.
Check AIR system. There should be no AIR to
ports while in "Closed Loop". See CHART C-6.
EGR valve: There should be no EGR at idle.
Run a cylinder compression check. See Section
"6". Inspect oxygen sensor for silicon contamination
from fuel, or use of improper RTV sealant. The
sensor will have a white, powdery coating, and
will 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.
Check for fuel in pressure regulator hose. If
present replace regulator assembly.
Check ignition system; wires, plugs, rotor, etc.
Check for loose or damaged air duct between
MAF sensor and throttle body.
Ilisconnect MAF sensor and if condition is
corrected replace sensor.
Clean injectors.
Monitoring block learn will help identify the
cause of the problem. If the system is runnig lean
(block learn greater than
138), refer to
"Diagnostic Aids" on facing page of Code
44. If
the system is running rich (block learn less than
118), refer to "Diagnostic Aids'' on facing page of
Code 45.

DRIVEABILITY AND EMISSIONS 2.8L (VIN S) 6E3-B-7
EXCESSIVE EXHAUST EMISSIONS 08 ODORS
Definition: Vehicle fails an emission test. Vehicle has excessive "rotten egg" smell.
Excessive odors do not necessarily indicate excessive emissions.
r Perform "Diagnostic Circuit Check."
e IF TEST SHOWS EXCESSIVE CO AND HC,
(or also has excessive odors):
@ Check items which cause car to run RICH.
@ Make sure engine is at normal
operating temperature.
@ CHECK:
- Fuel pressure. See CHART A-7.
- Incorrect timing. See vehicle emission
control information label.
- Canister for fuel loading. See CHART C-3.
- Injector balance. See CHART C-2A.
- PCV valve for being plugged, stuck, or
blocked PCV hose, or fuel in the crankcase.
- Spark plugs, plug wires, and ignition
components. See Section
"6D".
- Check for lead contamination of catalytic
converter (look for removal of fuel filler
neck restrictor).
- Check for properly installed fuel cap.
@ If the system is running rich, (block learn
less than
118), refer to "Diagnostic Aids" on
facing page of Code
45.
e IF TEST SHOWS EXCESSIVE NOx:
e Check items which cause car to run LEAN,
or to run too hot.
- EGR valve for not opening. See CHART
C-7.
- Vacuum leaks. - Coolant system and coolant fan for
proper operation. See CHART C-12.
- Remove carbon with top engine cleaner.
Follow instructions on can.
- Check ignition timing for excessive base
advance. See emission control
information label.
@ If the system is running lean, (block learn
greater than
138), refer to "Diagnostic Aids" on
facing page of Code
44.

6E3-C-1 2.8L (VIN S) DRIVEABILITY AND EMISSIONS
COMPONENT SYSTEMS
Section C provides information on the following:
@ General description of components and systems .
e On-vehicle service .
@ Part names and group numbers .
@ Diagnostic charts . These include a functional check of the system as well as diagnosis of any problem
found in the functional check
.
For locations of components. wiring diagrams and ECM Terminal End View refer to the front of the A Sections of
the engine being diagnosed
.
Following are the sub-section identification and the system covered:
Electronic Control Module (ECM) and Sensors
........................... Page C1-I
Fuel Control System ............................................... Page C2-1
Evaporative Emission Control (EECS) System ............................ Page C3-1
Ignition SystemIEST ............................................... Page C4-1
Air Injection Reaction (A.I.R.) System Manual Transmission Only .............. Page C6-1
Exhaust Gas Recirculation (EGR) System ................................ Page C7-1
Transmission Converter Clutch (TCC) System and Manual Transmission Shift Light Page C8-1
ECM Controlled Air Conditioning .................................... Page C10-I
Cooling Fan Control ............................................... Page C12-1
Positive Crankcase Ventilation (PCV) .................................. Page C13-1
DIAGNOSTIC CHARTS
The Diagnostic Charts for each system are found after the on-car service and parts information at the back of
each section
. Following are the charts found in this section .
@ Chart C-I
@ Chart C-1A
e ChartC-1E
@ Chart C-2A
e Chart C-2C
@ Chart C-3
@ Chart C-4A
@ Chart C-6
@ Chart C-7
@ Chart C-8
@ Chart C-8
@ Chart C-10
@ Chart C-12
@ Chart C-12 ECM
QDR Check ........................................... Page C1-10
Park
Neutral Switch ........................................ Page C1-12
Power Steering Pressure Switch Check .......................... Page C1-14
Injector Balance Test ....................................... Page C2-18
Idle Air Control ........................................... Page C2-20
Canister Purge Valve Check .................................. Page C3-4
Ignition System Check ...................................... Page C4-4
Electric Control (Divert) . (Manual Transmission) .................. Page C6-6
Exhaust Gas Recirculation Check .............................. Page C7-6
Automatic Transmission Converter Clutch (TCC) . 1 of 2 ............. Page C8-2
Automatic Transmission Converter Clutch (TCC) . 2 of 2 ............. Page C8-4
NC Clutch Control ......................................... Page C10-2
. ............. ............... Cooling Fan Control Circuit 1 of 2 Page C12-2
. ............................. Cooling Fan Control Circuit 2 of 2 Page C12-4

6E3-Cl-4 2.8L (VIN S) DRIVEABILITY AND EMISSIONS
BarWNeutral Switch (Auto Only)
The ParWNeutral (PIN) switch indicates to the
ECM when the transmission is in Park or Neutral.
This information is used for the TCC and the IAC
valve operation.
Important
Vehicle should not be driven with ParWNeutral
switch disconnected as idle quality will be affected
and a possible false Code
24 (VSS).
See Section "$A" for more information on the PIN
switch, which is part of the neutrallstart and backup
light switch assembly.
NC '"n" Signal
This signal tells the ECM that the A/C 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.
If this signal is not available to the ECM, idle may
be rough, especially when the
A/C compressor cycles.
The voltage at ECM terminal "B8" should equal
battery voltage when
AIC is requested and the
pressure cycling switch is closed.
The signal at
B8 will cause the ECM to turn on the
A/C clutch by energizing the A/C relay.
Distributor Reference Signal
The distributor sends a signal to the ECM to tell it
both engine RPM and crankshaft position. See EST
System for further information.
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
@ Remove fuse located in a weather proof holder
located near the battery for 30 seconds.
Since the ECM can have
a failure which may
effect 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:
€9
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 PROM is not correct for the
application.
- The incorrect components may cause a
malfunction and may or may not set a code.
@ The problem is intermittent. - This 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". Each driver is part of
a group of four called
"Quad-drivers". Failure of one driver can damage any
other driver in the set.
Solelloid and relay coil
resistance must measure more than 20 ohms. Less
resistance will cause early failure of the ECM
"driver". A shorted solenoid, relay coil, or harness,
with a GMP4 computer, will not damage the ECM, but
will cause the component to be inoperative.
Before replacing an ECM, be sure to check the coil
resistance of all solenoids and relays controlled by the
ECM. See ECM wiring diagram for the
solenoid(s)
and relay(s) and the coil terminal identification.
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 PROM 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 PROM.
@ 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 or
by a Code 55.
PROM
A faulty PROM may result in a Code 51.

DRIVEABILITY AND EMlSSlQNS 2.8L (VIN S) 6E3-C1-5
ECM Inputs
All of the sensors and input switches can be
diagnosed by the use of a "Scan" tool. Following is a
short description of how the sensors and switches can
be diagnosed by the use of "Scan".
The "Scan" can
also be used to compare the values for a normal
running engine with the engine you're diagnosing.
Coolant Temperature Sensor
A "Scan" tool displays engine temperature in
degrees centigrade. After
engine is started, the
temperature should rise steadily to about 90°C then
stabilize when thermostat opens. If the engine has not
been run for several hours (overnight) the coolant
temperature and MAT temperatures should read close
to each other. A fault in the coolant sensor circuit
should set a Code
14 or 15. The code charts also
contain a chart to check for sensor resistance values
relative to temperature.
MAF Sensor
A "Scan" tool reads the MAF value and displays it
in grams per second. Should read between 4-7 on a
fully warmed up idling engine. Values should change
rather quickly on acceleration, but values should
remain fairly stable at any given RPM. Most "Scan"
tools will have 2 positions for reading
MAE' sensor
values. (MAF
& Air Flow). Both values should read
the same if no Code 33 or 34 is set, but if a code is set,
the MAF values will be the default value and the Air
Flow parameter will lock in on the value to which the
ECM recognized the fault. A failure in the MAF
sensor or circuit should set a Code 33 or 34.
MAT Sensor
A "Scan" tool displays temperature of the air
entering the engine and should read close to ambient
air temperature when engine is cold, and rise as
underhood temperature increases. If the engine has
not been run for several hours (overnight) the MAT
sensor temperature and coolant temperature should
read close to each other. A failure in the MAT sensor
circuit should set
a Code 23 or 25. The code charts also
contain a chart to check for sensor resistance values
relative to temperature.
02 Sensor
The "Scan" has several positions that will indicate
the state of the exhaust gases,
O1! voltage, integrator,
and block learn. See "Scan" position information in
"Introduction," Section
"6E".
A problem in the O2 sensor circuit, or fuel system,
should set a Code 13 (open circuit), Code 44 (lean
indication), Code 45 (rich indication). Refer to
applicable chart if any of these codes
were stored in
memory.
TPS
A "Scan" tool displays throttle position in volts.
You should read
.55V f .08V, with throttle closed and
ignition on, or at idle. Voltage should increase at
a
steady rate as throttle is moved toward WOT.
The ECM has the ability to Auto-Zero the TPS
voltage if it is below about .7V (700
mV). This means
that any voltage less than
.7 volts will be determined
by the ECM to be
0% throttle. A failure in the TPS or
circuit should set a Code 21 or 22.
A "Scan" tools reading should closely match with
speedometer reading with drive wheels turning.
A
failure in the VSS circuit should set a Code 24.
PIN Switch
A "Scan" tool should read PIN when in Park, or
Neutral, and R-D, L, when in Drive or Overdrive.
This reading may vary with different makes of tools.
Refer to CHART
C-1A for PIN switch diagnosis.
NC Request Signal
"Scan" tool should indicate A/C request "ON,"
when A/C is requested and the pressure cycling switch
is closed.
Power Steering Pressure Switch
A "Scan" tool should read "OFF" normally and
"ON" with high pressure. This reading may vary with
different make of tools. Refer to CHART
C-1E for
PSPS diagnosis.
Reference Signal
A "ScanJ' tool will read this signal and is displayed
in rpm.
ON-CAR SERVICE
ELECTRONIC CONTROL MODULE (ECM)
Service of the ECM should normally consist of
either replacement of the ECM or a PROM change.
If the diagnostic
procedures call for the ECM to be
replaced, the engine calibrator (PROM) and ECM
should be checked first to see if they are the correct
parts. If they are, remove the PROM from the faulty
ECM
and install it in the new service ECM. THE
SERVICE ECM WILL NOT CONTAIN A PROM or
CALPAK. Trouble Code 51 indicates the PROM is
installed improperly or has malfunctioned. When
Code
51 is obtained, check the PROM installation for
bent pins or pins not fully seated in the socket. If it is
installed correctly and Code 51 still shows, replace the
PROM.

6E3-C1-6 2.8L (VIM O) DRlVEABlLlTY AND EMISSIONS
amportant
When replacing the production ECM with a
service ECM (controller), it is important to
transfer the Broadcast code and production
ECM number to the service ECM label. Please
do not record on ECM cover. This will allow
positive identification of ECM parts
throughout the service life of the vehicle.
amportant
To prevent internal ECM damage, the ignition
must be "OFF" when disconnecting or
reconnecting power to ECM (for example,
battery cable, ECM pigtail, ECM fuse, jumper
cables,
etc.).
ECM AND COMPONENTS REPLACEMENT
PROM OR ECM
Code 51 indicates a faulty PROM, possibly caused
by bent pins, or incorrect installation.
mmportant
It is possible to install a PROM backwards. If the
PROM
is installed backwards and the ignition key
turned to "ON," the PROM circuitry will be destroyed,
requiring PROM replacement.
NOTICE: The ignition should always be off when
installing or removing the ECM
connectors or internal components.
memove or Disconnect
1. Negative battery cable.
2. Right hand hush panel.
3. Connectors from ECM.
4. ECM mounting hardware.
5. ECM from passenger compartment.
6. ECM access cover (see Figure
C1-6).
7. Remove PROM assembly.
amportant
Using the rocker-type PROM removal tool,
enga& one end of t-hk PROM carrier with the
hook end of the tool (see Figure
C1-8). Press on
the vertical bar end of the tool and rock the
engaged end of the PROM carrier up as far as
possible. Engage the opposite end of the
PROM carrier in the same manner and
rock
this end up as far as possible. Repeat this
process until the PROM carrier and PROM are
free of the PROM socket.
The PROM carrier
with PROM in it Should lift off of the PROM
socket easily. PROM carrier should only
he
removed by using the pictured PROM removal
tool. Other methods could cause damage to the
PROM or PROM socket.
( ECM HARNESS
PROM CARRIER CONNECTORS TO ECM
1 PROM ACCESS COVER
Figure C1-6 PROM Access Cover
PROM CARRIER
PROM REMOVAL TOOL
Figure C1-7 PROM Removal Tool
Hnspect
1. New PROM for same part number as old.
Do not remove PROM from carrier to check PROM
number
2. For correct reference of PROM in carrier, Figure
C1-8.
3. CALPAK Assembly
Using the removal tool, pictured in Figure C1-9,
grasp the carrier
at the narrow ends. Gently rock the
carrier
from end to end while applying a firm upward
force and remove the CALPAK and carrier. Use of
unapproved
CAL,PAK removal tools or methods will
cause
damage to the CAI,PAK or CALPAK socket.