1988 PONTIAC FIERO engine oil

6E3-C2-20 2.8L (VIN S) DRIVEABILITY AND EMISSIONS
AIR THROTTLE FLOW BODY
LD START VALVE
8-5 BLUNVHT
BLUIBLK
GRMNVHT
. GRNIBLK
ECM
.
IAC COIL
"A" HI
IAC COIL "A" LO
IAC COIL "B" HI
C3 IAC COIL "B" LO
7-1 6-87
55 1800-6E
CHART C-2C
IDLE AIR CONTROL
2.8L (VIN S) ""F-SERIES (PORT)
Circuit Description:
The ECM will control engine idle speed by moving the IAC valve to control air flow around the throttle
plate. It does this by sending voltage pulses to the proper motor winding for each IAC motor. This will cause
the motor shaft and valve to move in or out of the motor a given distance for each pulse received. ECM pulses
are referred to as "counts".
@ To increase idle speed - ECM will send enough counts to retract the IAC valve and allow more air to flow
through the idle air passage and bypass the throttle plate until idle speed reaches the proper RPM. This
will increase the ECM counts.
@ To decrease idle speed - ECM will send enough counts to extend the IAC valve and reduce air flow through
the idle passage around the throttle plate. This will reduce the ECM counts.
Each time the engine is started and then the ignition is turned "OFF" the ECM will reset the IAC valve.
This is done by sending enough counts to seat the valve. The fully seated valve is the ECM reference zero. A
given number of counts are then issued to open the valve, and normal ECM control of IAC will begin from this
point. The
number of counts are then calculated by the ECM. This is how the ECM knows what the motor
position is for
a given idle speed.
The ECM uses the following information to control idle speed.
@ Battery voltage @ Engine Speed
@ Coolant Temperature @ A/C clutch signal
@ Throttle Position Sensor
Don't apply battery voltage across the IAC motor terminals. It will permanently damage the IAC motor
windings.
Test Description: Numbers below refer to circled Engine
idle speed can be adversely affected by the
numbers on the diagnostic chart. following:
1. Continue
with test even if engine will not idle. If @ ParUNeutral Switch - If ECM thinks the car is
idle is too low, "Scan" will display
80 or more always
in neutral, then idle will not be controlled
counts, or steps. If idle is high it will display
"0" to the specified rpm when in drive range.
counts.
@ Leaking injector(s) will cause fuel imbalance and
Occasionally an erratic or unstable idle may poor
idle quality due to excess fuel. See CHART
occur. Engine speed may vary
200 rpm or more up A-7.
and down. Disconnect
EAC. If the condition is @ Vacuum or crankcase leaks can affect idle.
unchanged, the IAC is not at fault. There is
a @ When the throttle shaft or throttle position sensor
system problem. Proceed to diagnostic aids below. is
binding or sticking in an open throttle position,
2. When the engine was stopped, the IAC valve the
ECM does not know if the vehicle has stopped
retracted (more air) to a fixed "Park" position for and does not control idle.
increased air flow and idle speed during the next
@ Check AIR management system for intermittent
engine start. A "Scan" will display
140 or more air
to ports while in "Closed Loop".
counts. @ In addition to electrical control of EGR, be sure to
3. Be sure to disconnect the IAC valve prior to this examine the
EGR valve for proper seating.
test. The test light will confirm the ECM signals @ Faulty battery cables can result in voltage
by a steady or flashing light on all circuits. variations. The
ECM will try to compensate,
4. There is a remote possibility that one of the CKTs which results in erratic idle speeds.
is shorted to voltage which would have been @ The ECM will compensate for A/C compressor
indicated by a steady light. Disconnect ECM and clutch
loads. Loss of this signal would be most
turn the Ignition "ON" and probe terminals to apparent
in neutral.
check for this condition.
@ Contaminated fuel can adversely affect idle. @ Perform in Diagnostic Aids: If all OK, refer to "Rough, Unstable, Incorrect Idle
or Stalling" "Svmptoms" in Section "B".

6E3-C4-2 2.8L (WIN S) DRIVEABILITY AND EMISSIONS
RESULTS OF INCORRECT OPERATION
An open or ground in the EST circuit will set a
Code 42 and cause the engine to run on the HE1
module timing. This will cause reduced performance
and poor fuel economy.
The ECM uses information from the
MAF and
coolant sensors in addition to rpm to calculate spark
~tdvance as follows:
@ Cold engine = more spark advance.
@ Engine under minimum load based on rpm
and low amount of air flow- more spark
advance. Hot engine
= less spark advance.
@ Engine under heavy load based on rprn and
high amount of air flow- less spark advance.
The description, operation, and diagnosis of the
HE1 system are found in Section "GD" of this manual.
CODE 12
Code 12 is used during the Diagnostic Circuit
Check procedure to test the code display ability of the
ECM. This code indicates that the ECM is not
receiving the engine
rpnl (REFERENCE) signal. This
occurs with the ignition key "ON" and the engine not
running.
The "Reference" signal also triggers the fuel
injection system. Without the "Reference" signal the
engine cannot run.
OM-CAR SERVICE
SETTING TIMING
The initial base timing is set by disconnecting the
timing connector, located near the blower motor.
Refer to Emission Control Information Label for
procedure.
This will cause Code 42 to store in the code
memory of the ECM.
The memory must be cleared
after setting timing.
How Code 42 Is Determined
When the system is running on the HE1 module,
that is no voltage on the bypass line, the
HE1 module
grounds the EST signal.
The ECk1 expects to see no
voltage
on the EST line during this condition. If it sees
a voltage, it sets code 42 and will not go into the EST
mode.
When the rpm for EST
is reachecl bout 300 rprn)
the ECM applies 5 volts to the bypass line and the E:SrI'
should no longer be grounded in the tIEI nodule so
the EST voltage should be varying.
If the bypass line is open or grounclecl, the IIEI
tnod~lle will not switch to EST mode so the EST
voltage will be low
and Code 42 will be set. Refer to
Section
"611" for on vehicle service.
PARTS INFORMATION
PART NAME GROUP
Controller, ECM
(Remanufi~ctured) ................ 3.670
.......................... Distributor 2.36 1
Module, Distr ........................ 3.380
........................... Coil, Distr 2.170

6E3-C6-2 2.8L (WIN 5) DRIVEABILITY AND EMISSIONS
When the solenoid is de-energized, the pressurized
air from the air pump is allowed to enter the decel
timing chamber. This places sufficient pressure on
the metering valve diaphragm to overcome spring
tension, closing the
valve,causing air to divert to the
silencer.
At higher engine speeds, excess air is exhausted to
the silencer through the pressure relief valve. (Figure
C6-1)
Deceleration Valve
To help prevent backfiring during high vacuum
conditions a deceleration (gulp) valve is used to allow
air to flow into the intake manifold (shown in Figure
C6-2). This air enters the airlfuel mixture to lean the
rich condition created by high vacuum when the
throttle valve closes on deceleration.
The vacuum draws the deceleration valve
diaphragm down and opens the valve allowing air
inlet duct to flow into the intake manifold.
RESULTS OF INCORRECT OPERATION
@ If no air (oxygen) flow enters the exhaust stream
at the exhaust ports, HC and
CO emission levels
will be too high.
@ Air flowing to the exhaust ports at all times could
cause
a rich ECM command and increased
temperature of the converter. This may also cause
a Code
44 due to oxygen being pumped passed the
oxygen sensor. There should be no air going to the
exhaust ports while operating in the closed loop
mode.
DIAGNOSIS
The diagnosis of the AIR system is covered in
CHART C-6 at the end of this section.
OPERATIONAL CHECKS
A.I.R. Pump
1. The air pump is a positive displacement vane type
which is permanently lubricated and requires no
periodic maintenance.
Accelerate engine to approximately
1500 rpm's
and observe air flow from
hose(s). If air flow increases
as engine is accelerated, pump is operating
satisfactorily. If air flow does not increase or is not
present, proceed as follows:
Inspect
For proper drive belt tension.
2. For a leaky pressure relief valve. Air may he
heard leaking with the pump running.
DECELERATION VALVE
1 VACUUM BLEED VALVE
1 MANIFOLD VACUUM
1 DECELERATION AIR TO INTAKE
MANIFOLD
1 FILTERED AIR FROM INTAKE DUCT
/ DIAPHRAGM
05 10 84 5s 1726-6E
Figure C6-2 - Deceleration Valve
NOTICE: If the engine or underhood compartment
is to he cleaned with
steam or high-
pressure detergent, the centrifugal filter
fan should be masked "OFF7' to prevent
liquids from entering the pump.
Inspect
3. For a seized Air Injection Pump.
3. Hoses, tubes and all connections for leaks and
proper routing.
5, For air flow from controllswitching valve.
6. AIR injection pump for proper mounting and bolt
torque.
7. If no irregularities exist and the AIR injection
pump noise is still excessive, remove and replace
pump.
CAUTION: Do Not Oil Air Pump
Hoses and Pipes
Inspect
1. Hose or pipe for deterioration or holes.
2. All hoses or pipe connections, and clamp tightness.
3. Hose or pipe routing. Interference may cause
wear

6E3-C8-2 2.8L (VIN S) DRIVEABILITY AND EMISSIONS
VEHICLE SPEED SIGNAL
SPEED INPUT
CONNECTOR
aTH GEAR SIGNAL
422 TAN/BLK
4TH GEAR SW.
TRANSMISSION
ALDL CONNECTOR
TCC APPLY SOLENOID
CHART C-8
(Page 1 of 2)
AUWBMATIC TRANSMISSION CONVERTER CLUTCH (TCC)
2.8L (VIN S) "F" SERIES (PORT)
Circuit Description:
The purpose of the automatic transmission torque converter clutch feature is to eliminate the power loss of
the torque converter stage when the vehicle is in a cruise condition. This allows the convenience of the
automatic transmission and the fuel economy of a manual transmission. The heart of the system is
a solenoid
located inside the automatic transmission which is controlled by the
ECM.
When the solenoid coil is activated ("ON"), the torque converter clutch is applied which results in straight
through mechanical coupling from the engine to transmission. When the transmission solenoid is deactivated,
the torque converter clutch is released which allows the torque converter to operate in the conventional manner
(fluidic coupling between engine and transmission).
The ECM turns
"ON" the 'KC when coolant temperature is above 65°C (14g°F), TPS not changing, and
vehicle speed above a specified value.
Test Description: Numbers below refer to circled Diagnostic Aids:
numbers on the diagnostic chart. A "Scan" tool only indicates when the ECM has 1. When a test light is connected from ALDL turned the TCC driver (grounded CKT 422), but terminal "F" to ground, a test light "ON" indicates
this does not confirm that the TCC has engaged. To battery voltage is OK and the TCC solenoid is
determine if TCC is functioning properly, engine rpm
disengaged.
should decrease when the "ScanJ' indicates the TCC
2. When the diagnostic terminal is grounded, the
driver has turned "ON". To determine if the 4th gear ECM energize the TCC "Ienoid and the switch is functioning properly, perform the checks in
test light should go out.
CIIART C-8A (Page 2 of 2). The switches will not
prevent TCC fi-om functioning but will affect TCC lock
and unlock points. If the 4th gear switch CKT is
always open the
TCC may engage as soon as sufficient
oil
pl.essure is reached.

6E3-C10-2 2.8L (VIN S) DRIVEABILITY AND EMISSIONS
A/C CONTROL
DK GRNNVHT 59
CHART C-10
AIC CLUTCH CONTROL
2.8L (VIN S) "F" WRIES (PORT)
Circuit Description:
ECM control of the A/C clutch improves idle quality and performance by:
Delaying clutch apply
until the idle air rate is increased.
e Releasing clutch when idle speed is too low or during high power steering loilds.
e Releasing clutch a1 wide open throttle.
smooths cyclingof the compressor by providing additional fuel at the instant clutch
is applied.
Voltage is supplied to the
NC Clutch Control relay on CKT 59 by the NC Control Switch. This saine
voltage is supplied as a signal to ECM pit1 88. After a time delay of about 112 second the ECM twill ground
terminal
"A2," CKT 905, and close the A/C relay contacts.
When
relay is energi~etf battery vollage from CKT 59 is supplied to the IVC clulch lhroug11 Ihe txlay arid
CKT 959.
Test Description: Numbers below refer to circled
numbers on the diagnostic chart.
1. The ECM will only energize the A/C relay, when
the engine is running.
'I'his lest will determine if
the relay, or CK'F 905, is Sauity.
2. In order for the clutch to proper1.y be engaged, the
pressure cycling switch must bc closc!cl to provide
12 volts to the relay,
ilnd the high pressure switch
must be closed, so the
AlC rtquest (12 volts) wlll
be present at the ECNI.
3. Determines if the signal is ~.eachitlg the I4:CAI on
CKT 59 from the A/C control panel. Signal hhoitld
only be present when the AlC mode or tlcl'rost
mode has been selected.
4. A short to ground in any part ot' the A/C request
circuit, CKT
67 to the relay CKrI' 59, CKT 959 to
the NC clutch, or the
:2/C clutch, coulcl be the
cause
ofthe blown fiise.
5. With the ignition "ON" and the diagnostic
tcrminal grounded, the ECM should be grounding
CKT 905 which should cause the test light to be
"ON".
Diagnostic Aids:
If complaint was insufficient cooling, the problem
111~1,~ be ciiuscd by an inoperalive cooling fan. 'I'he
t!11gine cooling fan should turn "ON," when AlC is
"ON" ,tntl cZ/C head pressure exceeds about 233 psi. If
not. qctt: ("I Iclli'I' C-12 for diagnosing the cooling fan.

CONNECTOR
TO ALTERNATOR
I.P.CONNECTOR
DK GRNNVHT 335
CHART C-12
(Page 1 of 2)
COOLING FAN CONTROL CIRCUIT
2.8L (VIN S) "F" SERIES (PORT)
Circuit Description:
'I'he electric cooling fan is controlled by the ECM, based on inputs from the coolant temperature sensor, the
NC fan control switch, and vehicle speed. 'I'he ECM controls the f~in by grounding CKT 335, which energizes
the fan control relay. Battery voltage is then supplied to the fan motor.
The ECM grounds
CKT 335, when coolant temp. is over about 106°C (223"F), or when AIC has been
requested, and the fan control switch opens with high
I\/C pressure, about 200 psi (1380 kPa). Once the ECM
turns the relay "ON", it will keep it "ON" for a nlinirnum of GO seconds, or until vehicle speed exceeds 70 mph.
Also, if Code
14 or 15 sets, or the ECM is in throttle body back up, the fan will run at all times.
On
kt vehicle not equipped with A/C, CK'I' 732 is,ju~rlperetl to ground so that Lhe fan does not run at all times.
Test Description: Numbers below refer to circled
numbers on the diagnostic chart,.
1. With the diagnostic terminal grounded, the
cooling
fan control driver will close, which should
energize the fan control
relay.
2. If the A/C fan control switch or circuit is open, the
fan would run whenever the engine is running.
3. With AIC clutch engaged, the i\lC fan control
switch should open, when
A/C high pressure
exceeds about
200 psi ( 1380 k13a). This signal
should cause the
ECM to energize the ran control
relay.
Diagnostic Aids:
If the owner complained of an overheating
problem, it
rnust he determined if the complaint was
clue to an actuill hoilover, or the hot light, or
temperature gage indicated over heating.
If the gage, or light, indicates overheating, but no
hoilover is detected, the gage circuit should he
checked.
'I'he gage accuracy can, also, be checked by
comparing the coolant sensor reading using a "Scan"
tool and comparing its reading with the gage reading.
If the engine is actually overheating, and the gage
indicates overheating, but the cooling fan is not
coming "ON", the coolant sensor has probably shifted
out
ofcalibration and should be replaced.
If
the engine is overheating, and the cooling fan is
"ON", the cooling system should hc checked.

DRIVEABILITY AND EMISSIONS 2.8L (VIN S) 6E3-C13-1
SECTION C13
POSITIVE CRANKCASE VENTILATION (PC\/)
.... GENERAL DESCRIPTION ................ C13-1 FUNCTIONAL CHECK OF PCV VALVE C13-1
RESULTS OF INCORRECT OPERATION .... C13-1 ON-CAR SERVICE ..................... C13-2
DIAGNOSIS
......................... C13-1 PARTS INFORMATION ................. C13-2
GENERAL DESCRIPTION 4. Turn "OFF" the engine and remove PCV valve.
Shake valve and listen for the rattle of check
A "closed" crankcase ventilation (PCV) system is needle inside
the valve. If valve does not rattle,
used to provide more complete scavenging of replace
v4 ~1 1 ve.
crankcase vapors. Fresh air from the air cleaner is With this
system, any blow-by in excess of the
slipplied to the crankcase, mixed with blow-by gases system capacity (from a badly-worn engine, sustained
and then passed through a positive crankcase heavy load, etc.) is exhausted into the air cleaner and
ventilation
(PCV) valve into the intake manifold isdrawn into theengine.
(Figure C13-1).
The primary control is through the PCV valve
(Figure
(213-2) which meters the flow at a rate
depending on manifold vacuum.
To maintain idle quality, the PCV valve restricts
the flow when intake manifold vacuum is high. If
abnormal operating conditions arise, the system is
designed to allow excessive amounts
of I,low-by gases
to back flow through the crankcase vent tube into the
engine air inlet to be consumed by normal combustion.
RESULTS OF INCORRECT OPERATION
A plugged valve or hose may cause:
@ Rough idle.
@ Stalling or slow idle speed.
@ Oil leaks.
@ Sludge in engine.
A leaking valve or hose would cause:
@ Rough idle.
@ Stalling.
@ Iiigh idle speed.
DIAGNOSIS
FUNCTIONAL CHECK OF PCV VALVE
If an engine is idling rough, check for a clogged
PCV valve or plugged hose. Replace as required. Use
the following procedure:
1. Remove PCV valve from rocker arm cover.
2. Run the engine at idle.
3. Place your thumb over end of vi~lcce to check for
vacuum. If there is
no vacuum at valve, chcck for
plugged hoses or
lrlanifold port, or 1'CV valve.
Replace plugged or dcterioratcd hoses.
a CLEAN AIR
VOLATILE OIL FUMES
---e- MIXTURE OF AIR AND FUMES
PCV VALVE
1 TO THROTTLE BODY
CRANKCASE VENT HOSE
1 PCV VALVE HOSE
150 INTAKE MANIFOLD
Figure C13-1 PCV Flow

6E3-C13-2 2.8L (VIN 5) DRIVEABILITY AND EMISSIONS
Proper operation of the PCV System is dependent ON-CAR SERVICE
upon a sealed engine. If oil sludging or dilution is
noted, and the PCV System is functioning properly,
An engine which is operated without any
check engine for possible cause and correct
to ensure crankcase ventilation can be damaged. Therefore, it is
that system will function as intended.
important to replace the PCV valve at
intervals
shown in Section
"OB".
Periodically, inspect the hoses and clamps and
replace any showing signs of deterioration.
I I PARTS INFORMATION
PART NAME GROUP
Figure C13-2 PCV Valve Cross Section
......................... Air Cleaner 3.402
............... Valve Asm, C/Case Vent 1.745
.................... Tube, C/Case Vent 1.762
................ Hose, C/Case Vent V 1 v 1.762
.................. Breather, NC and Sil 3.410