1988 PONTIAC FIERO Service Repair Manual

NEGATIVE BACKPRESSURE EGR VALVE
The valve on this engine is called a negative
backpressure valve. It varies the amount of exhaust
gas flow into the manifold depending on manifold
vacuum and variations in exhaust backpressure.
The diaphragm on this valve (shown in Figure
C7-2) has an internal vacuum bleed hole which is held
closed by
a small spring when there is no exhaust
backpressure. The amount of vacuum to the valve is
controlled by the
ECM controlling a solenoid.
Engine vacuum opens the EGR valve against the
pressure of
a large spring. When manifold vacuum
combines with negative exhaust backpressure, the
vacuum bleed hole opens and the EGR valve closes.
EGR VALVE AIR BLEED
EXHAUST GAS HOLE
INTAKE AIR SMALL
SPRING
VACUUM PORT LARGE
SPRING
Figure C7-2 - Negative Backpressure EGR Valve
EGR VALVE IDENTIFICATION
@ Negative backpressure EGR valves will have an
"N" stamped on the top side of the valve after the
part number (Figure
C7-3).
@ Positive backpressure EGR valves will have a "P"
stamped on the top side of the valve, after the part
number.
@ Port EGR valves have no identification stamped
after the part number.
When replacing an
EGIE valve, always check for
correct part number in the parts catalog or
supplemental bulletin.
Figure C7-3 - EGR Valve Identification
RESULTS OF INCORRECT OPERATION
Too much EGR flow tends to weaken combustion,
causing the engine to run roughly or stop. With too
much EGR flow at idle, cruise, or cold operation,
aliy
of the following conditions may happen:
@ Engine stops after cold start.
@ Engine stops at idle after deceleration.
@ Car surges during cruise.
@ Rough idle.
If the EGR valve should stay open all of the time,
the engine may not idle.
Too little or no EGR flow allows combustion
temperatures to get too high during acceleration and
load conditions. This could cause:
@ Spark knock (detonation).
@ Engine overheating.
@ Emission test failure.
DIAGNOSIS
Diagnosis of the EGR system is covered in CHART C-7
at the end of this section.
EGR VALVE
Remove or Disconnect
1. Plenum (See Plenum R&R).
2. Vacuum line.
3. Retaining bolts.
4. EGR valve.
Install or Connect
1. Reinstall valve or replacement EGR valve on
intake manifold using new gasket.
2. Bolts and tighten to 18 N.m (14 Ib. ft.).
3. Vacuum line to valve.
4. I'lenum.

DRIVEABILITY AND EMISSIONS 5.OL (VIN F) & 5.7L (VIN 8) 6E3-C7-3
1. With a wire wheel, buff the exhaust deposits from
the mounting surface and around the valve.
2. Look for exhaust deposits in the valve outlet.
Remove deposit build-up with a screwdriver.
3. Clean mounting surfaces of intake manifold and
valve assembly.
EGR SOLENOID 1 EGR VALVE
121 COIL 151 BOLTS (2)
ls] BOLT (2) 21 N.m EGR DlAG TEMP SWITCH
(16 FT. LBS.) 12 N.m (105
IN. LBS.)
Figure C7-4 - EGR and Solenoid Service
EGR Manifold Passage
Inspect
If EGR passages in the inlet manifold indicate
excessive build-up of deposits, the passages should be
cleaned. Care should be taken to ensure that all loose
particles are completely removed to prevent them
from clogging the EGR valve or from being ingested
into the engine.
Do not wash EGR valve in solvents or degreaser--
permanent damage to valve diaphragm may result.
Also, sand blasting of the valve is not recommended
since this can affect the operation of the valve.
EGR CONTROL SOLENOID
Remove or Disconnect
1. Negative battery cable.
2. Electrical connector at solenoid
3. Vacuum hoses.
4. Nut and solenoid.
Install or Connect
1. Solenoid and bracket, tighten nut to 24 N-m
(17 1b. ft.).
2. Vacuum hoses.
3. Electrical connector.
4. Negative battery cable.
PARTS INFORMATION
PARTS NAME GROUP
Control, EGR Vacuum ................ 3.670
Gasket, EGR Valve .................. 3.680
Valve, EGR ........................ 3.670

6E3-C7-4 5.OL (VIN F) €4 5.7L (VIN 8) DRIVEABILITY AND EMISSIONS
CHART C-7
EXHAUST GAS RECIRCULATION CHECK
5.OL (VIN F) & 5.7L (VIN 8) "F" SERIES (PORT)
Circuit Description:
The exhaust gas recirculation (EGR) valve is controlled by a normally open pulse width modulated (PWM)
solenoid. The ECM turns the solenoid "OFF" to allow vacuum to pass to the EGR and turns the solenoid "ON"
to prohibit EGR operation. When EGR is commanded, the solenoid is turned "ON" and "OFF" many times a
second (duty cycle).
The duty cycle is calculated by the ECM based on information from the coolant, MAT, TPS, and MAF
sensors. Also, engine
rpm's and the PIN switch input affect EGR.
There should be no EGR when in park or
neutral, TPS below
a calibrated value or TPS indicating WOT.
With the ignition "ON" and engine stopped, the EGR solenoid is de-energized. The solenoid, however,
should be energized if the diagnostic terminal is grounded with the ignition "ON" and engine not running.
Test Description: Numbers below refer to circled 2. As soon as back pressure is available at the EGR
numbers on the diagnostic chart.
valve, the bleed portion in the valve should open
1. This will test the solenoid value to determine if it
and cause the valve to go to its heated position.
is capable of closing off the manifold vacuum from
3. 'I'he EGR will be inoperative if the PIN switch is
the EGR valve. The vacuum may bleed off slowly
misadjusted or faulty. Use "Scan" tool and check
but this should not be considered a fault.
PIN switch. Refer to CHART C-1.

6E3-C7-6 5.OL (VIN F) & 5.7L (WIN 8) DRIVEABILITY AND EMISSIONS
BLANK

DWlVEABlLlTV AND EMISSIONS 5.01, QVIN F) & 5.71 (VIN 8) 6E3-C8-1
TRANSMISSION CONVERTER CLUTCH (KC) SYSTEM
AND MANUAL "TRANSMISSION SHlFT LBGH"O"=Ob ONLY
CONTENTS
................ GENERAL DESCRIPTION C8-1 DIAGNOSIS ....................... .. C8-1
........ PURPOSE ......................... CS-1 SHIFT LIGHT (MIT) DESCRIPTION C8-1
....................... OPERATION C8-1 DIAGNOSIS ......................... CS-1
OM-CAR SERVICE ..................... C8-1
GENERAL DESCRIPTION
PURPOSE
The transmission converter clutch (TCC) system
uses
a solenoid operated valve in the automatic
transmission to couple the engine flywheel to the
output shaft of the transmission thru the torque
converter. This reduces the slippage losses in the
converter, which increases fuel economy.
OPERATION
For the converter clutch to apply, two conditions
must be met:
e Internal transmission fluid pressure must be
correct. For information on internal transmission
operation, see Section
"7A". This section will
cover only the electrical operation of the TCC
system.
@ The ECM grounds a switch internally to turn
"ON" a solenoid in the transmission. This moves a
check ball, which will allow the converter clutch
to apply, if the hydraulic pressure is correct, as
described above.
The ECM controls the TCC apply solenoid by
looking at several sensors:
@ Speedo Buffer Sensor (also called Vehicle Speed
Sensor
(VSS) Speed must be above a certain value
before the clutch can apply.
@ Coolant Temperature Sensor Engine must be
warmed
LIP before clutch can apply about 65" C
(149°F).
Throttle Position Sensor (TPS) After the
converter clutch applies, the ECM uses the
information
from the TPS to release the clutch
when the car is accelerating or decelerating at
a
certain rate.
The brake switch
is also part of the 'I'CC circuit as
it will remove battery voltage to the
'FCC solenoid
when the brake pedal is depressed.
@ Gear Select Switch The 4th gear switch is used to
send a signal to the ECM telling it when the
transmission is in 4th
gear
The ECM uses this information to vary the conditions
under which the clutch applies or releases. However,
the transmission does not have to be in fourth gear in
order for the ECM to turn the clutch "ON".
If the converter clutch is applied at all times, the
engine will stall immediately, just as in a manual
transmission with the clutch applied.
If the converter
clutch does not apply, fuel
ecomony may be lower than expected. If the vehicle
speed sensor fails, the TCC will not apply. If the 4th
gear switch does not operate, the TCC may not apply
at the right time.
DIAGNOSIS
The diagnosis of the TCC system is covered in
CHART C-$A. If the ECM detects a problem in the
system, a Code 24 should set. In this case, see Code 24
CHART.
SHIFT LIGHT (MR) DESCRIPTION
The purpose of the shift light is to provide a
display which indicates the optimum fuel economy
point for up shifting the manual transmission based
on engine speed and load. The display is
a lamp on the
instrument panel. Activation
of the ECM driver turns
the lamp "ON".
DIAGNOSIS
The shift light circuit can be checked using
CEIAR'I' C-8B.
ON-CAR SERVICE
See Section "8B" if the shift light bulb needs
replacement.
See Section
"GE" to repair wiring problem.
@ See Section "C- 1" if ECM is to be replaced.

6E3-C8-2 5.OL (VIN F) & 5.7L (VIN 8) DRIVEABILITY AND EMISSIONS
15-WAY I.P. CONNECTOR
VEHICLE SPEED SIGNAL
SPEED INPUT
4TH GEAR SIGNAL
422
TANIBLK
4TH GEAR SW.
TRANSMISSION ALDL CONNECTOR
TCC APPLY SOLENOID
CHART C-8A
(Page 1 of 2)
AUTOMATIC TRANSMISSION CONVERTER CLUTCH (TCC)
5.OL (VIN F) & 5.7L (VIN 8) "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 TCC when coolant temperature is above
65" C (149" F), TPS not changing ,and
vehicle speed above
a specified value.
Test Description: Numbers below refer to circled Diagnostic Aids:
nbers on the diagnostic chart.
When
a test light is connected from ALDL
terminal "F" to ground, a test light "ON" indicates
battery voltage is
OK and the TCC solenoid is
disengaged.
When the diagnostic terminal is grounded, the
ECM should energize the TCC solenoid and the
test light should go out.
A "Scan" tool only indicates when the ECM has
turned "ON" the TCC driver (grounded CKT
422) but
this does not confirm that the TCC has engaged. To
determine if TCC is functioning properly, engine rpm
should decrease when the "Scan" indicates the TCC
driver has turned "ON". To determine if the 4th gear
switch is functioning properly, perform the checks in
CHAW C-8A (Page 2 of 2). The switches will not
prevent TCC
from functioning but will affect TCC lock
and unlock points. If the 4th gear switch circuit is
always open, the TCC may engage as soon as
si~t'ficient oil pressure is reached.

DRIVEABILITY AND EMISSIONS 5.OL (VIN F) & 5.7L (VIN 8) 6E3-C8-3
DRIVE WHEELS TURNING. IF CODE 24
OULD GO OUT.