check engine NISSAN 300ZX 1984 Z31 Engine Fuel And Emission Control System Workshop Manual

DIAGNOSTIC PROCEDURE
b NG 3 Check idle speed and ignition timing
Driveability
(--- START -l
Adjust to specifications
4 Check mixture ratio feedback system Clean injectors or adjust to specifications
I 5 Perform driveability test I
OK NG
Repair or replace components as necessary
P
6 Perform electronic control system inspection
OK I
Adjust to specifications
OK 1 I
NG 4-
7 Check idle mixture ratio
, I
I
Replace air flow meter. 8 Check mixture ratio at middle engine NG
speed
OK
) 9 Perform driveability test
EF & EC-29

DIAGNOSTIC PROCEDURE
Driveabil
1. Inspect engine and E C C.S. for air leaks,
proper electrical connections, etc
1) Check all hoses and ducts for air leaks
2) Check air cleaner for clogging
3) Check harness connectors for proper connec-
tions
4) Check ignition wiring
5) Check gaskets for leaks at all air intake com-
ponents
6) Check E G.R valve operation
7) Check air regulator operation
2 Perform E C C S self-diagnosis
Follow the procedure in E CCS SELF-
DIAGNOSIS (Page EF & EC-35)
3 Check idle speed and ignition timing
a. Prepare the following conditions:
Headlampswitch' OFF
Heater blower: OFF
Air conditioner switch: OFF
Front wheel (Power steering model):
KEEP STRAIGHT AHEAD
b. Warm engine to operating temperature.
Check
and adjust as follows
[VG30E engine (Without turbocharger)]
1) Stop engine and disconnect idle-up solenoid
valve harness connector
Idle-up solenoid
2) Start engine and race engine two or three times
under no-load, then run engine
at idle speed
(Cont'd)
3) Check idle speed
M/T & A/T (in "D" position)
700250 rpm at sea level
650250 rpm at high altitude condition
If necessary, adjust to the specified
speed by
turning idle speed adjusting screw
I, SEF6456
4) Stop engine and connect idle-up solenoid valve
harness connector
5) Start engine and check ignition timing with
a
timing light
20ai2" B.T.D.C.
If necessary, adjust ignition
timing by turning
distributor
[VG30ET engine (With turbocharger)]
1) Race engine two or three times under no-load,
then run engine at idle speed
2) Check idle speed.
M/T: 70W50rpm
A/T: 650k50 rpm (in "D" position)
EF & EC-30

DIAGNOSTIC PROCEDURE
Driveabili
If out of specification, adjust as follows
ness connector
a Stop engine and disconnect A A C valve har-
SEF646B
b Start engine and adjust engine speed by turning
idle speed adjusting screw
M/T: 650 rpm
A/T. 600 rpm (in "D" position)
c. Stop engine and connect A.A.C. valve har-
ness connector Then
start engine
d Make sure that idle speed
is in the specified
range.
3) Check ignition timing with a timing light
ZO"r2" B.T.D.C.
If necessary, adjust ignition timing by turning
distributor
Perform mixture ratio feedback
system inspec-
tion Follow the procedure
in MIXTURE RATIO
4
(Cont'd)
FEEDBACK SYSTEM INSPECTION (Page EF
lk EC-60)
5 Perform driveability test
Evaluate effectiveness of adjustments by driv-
ing vehicle If unsatisfactory, proceed to step
6
6
Perform electronic control system inspection
Check the following using circuit tester
Injector circuits
Air regulator circuit
E G R control solenoid circuit
E xhaust gas sensor heater circuit
Follow the procedure in ELECTRONIC CON-
TROL SYSTEM INSPECTION (Page EF
& EC-
43)
7 Check idle mixture ratio
1) Warm up engine to operating temperature
2) Turn off engine and disconnect throttle valve
switch harness connector
3) Verify that the diagnosis mode selector is
turned fully counterclockwise
4) Start engine and verify that engine IS still at
operating temperature.
5) Race engine two or three times under no-load,
then run engine
at idle speed
6) Look at inspection lamps (red and green)
SEF648B
When both inspection lamps blink, it indicates
that the idle mixture ratio IS correct.
EF & EC-31

DIAGNOSTIC PROCEDURE
Driveability (Cont'd)
7) If N G., adjust idle mixture ratio by turning
variable resistor on
air flow meter so that
inspection lamps blink simultaneously
SEF649B
B Check mixture ratio at middle engine speed
1) Verify that inspection lamps on control unit
blink simultaneously at idle.
2) Race engine two or three times under no-load,
then run engine
at idle speed
3) Gradually increase engine speed and check for
operating (blinking)
of the inspection lamps at
different engine rpms (up to approximately
2,000 rprn).
If both inspection lamps continue to blink
during idle to
2,000 rpm range, it indicates that
the idle mixture ratio is correct
4) If N.G., replace air flow meter and adjust idle
mixture ratio
as per step 7
5) Turn off engine and connect throttle valve
switch harness connector
9. Perform driveability test
Reevaluate vehicle performance.
EF %t EC-32

DIAGNOSTIC PROCEDURE
5 Check idle mixture ratio
Improper Idling and Stall
START 2
N.G Clean injectors or adjust to specifications
Locare ano repair
1
NG 4 I
2 Perform E C C S self-diagnosis Repair or replace components as necessary J OK
Adjust to specifications NG 3 Check idle speed and ignition timing
OK Adjustable adjustable
4 Perform electronic control system inspection
OK I
1. Inspect engine and E C C S for air leaks, elec-
tric connections, etc
Refer to DRIVEABILITY
Perform
E C C S self-diagnosis
Follow the procedure in E.CCS. SELF-
DIAGNOSIS
(Page EF & EC-35).
3 Check idle speed and ignition timing.
Refer to DRIVEABILITY
4. Perform electronic control system inspection.
Check the following using circuit tester
Injector circuit
Air regulator circuit
A.A.C. valve (With turbocharger)
2
Idle-up solenoid valve (Without turbocharger)
E G R. control solenoid circuit
Follow the procedure in ELECTRONIC CON-
TROL SYSTEM INSPECTION (Page EF
& EC-
43)
Refer to DRIVEABILITY
5. Check idle mixture ratio.
EF & EC-33

DIAGNOSTIC PROCEDURE
c
Engine Startability
1 Check starting system and battery
charging system NG 4 Repair or replace components as necessary 1
OK I
__c NG 3 Check ignition system
NG 2 Check fuel level Supply fuel
OK 1
Repair or replace components as necessary
I
4 Perform E C C S sel Repair or replace components as necessary
5 Perform electronic control system inspection
Locate and repair
1. Check starting system and battery charging
1) Check starter operation
2) Check battery voltage.
2 Check fuel level
3 Check ignition system.
1) Check ignition wiring
2) Check distributor rotor head
3) Check spark plug
4 Perform
E C C.S. self-diagnosis. Follow the
procedure in E.C.C.S. SELF-DIAGNOSIS (page
Perform electronic control system inspection.
Check the following using circuit
tester.
system
Repair or replace as necessary.
If fuel level is low or empty, add fuel
EF & EC-35)
5
Injector circuit
Air regulator circuit
E G.R control solenoid valve
Follow the procedure
in ELECTRONIC CON-
TROL SYSTEM INSPECTION (page EF & EC-
43)
Inspect engine and E CCS for air leaks
Refer to DRIVEABILITY
EF & EC-34

SELF-DIAGNOSIS
Self-diagni
The self-diagnostic system determines malfunctions
of signal systems such as sensors, actuators, and
wire harnesses based on the status of the input
signals received by the
E C C S control unit
A malfunction is displayed by both the red and
green
L E D s (Light Emitting Diodes).
Basically, self-diagnosis
is always performed when
the power
is furnished to the E C C S control
unit The self-diagnosis results
are retained in the
memory chip of the
E C C S control unit and are
displayed only when the diagnosis mode selector
(located on
the side of the E C C S. control unit) is
turned fully clockwise
The self-diagnostic system
is provided with func-
tions which display malfunctions being checked
as well as those which are stored in the memory
In
this sense, it is very effective in determing an
"intermittent" malfunction The results which
is
or was stored in the memory can be erased by
following the steps specified
A malfunctioning area is determined by the num-
ber of blinks of both the
red and green L E D s
First, the red L E D blinks and the green follows
The red L E D refers to the tenth digit while the
green
one refers to the unit digit. For example,
when the red L
E D. blinks three times and the
green
L E.D blinks twice, this implies number
"32" In this way, all problems are classified by
code numbers.
inspection lamps1 Diagnosis mode
SEF6508
Judging the selfdiagnosis results
1 When the ignition switch is turned "ON",
the diagnostic system judges
a malfunction
tic System
until the specified input signal is entered and
detected
as 0 K
(These input signals are not stored in the
memory
)
1) Vehicle speed sensor circuit (VG30ET engine)
When the vehicle speed exceeds
10 km/h
(6 MPH) and its corresponding signal is entered
2) Throttle valve switch (idle switch) circuit,
neutral switch circuit (VG30ET engine) and
air
conditioner switch circuit
After the ignition switch
is turned "ON" and
"ON-OFF"
signals from each switch are
entered
3) Start signal
After the engine has started and when start
signals "ON" and then "OFF" are entered
2 After the self-diagnostic system has detected
a malfunction, it continues to provide a mal-
function display until the memory
is erased
properly by the sepcified steps
1) Crank angle sensor circuit
When 1" or 120" signal is not entered after
the engine has started
When either 1" or 120" signal is not entered
often enough
2) Air flow meter circuit
When the air flow meter produces an abnormal-
ly high output voltage with the engine off
When the air flow meter produces an abnormal-
ly low output voltage with the engine running.
3) Cylinder head temperature sensor circuit
When the cricuit
is shorted or open
4) Ignition signal
When an ignition signal
is not produced on the
primary winding of the ignition coil after
the
engine has started
5) Fuel pump circuit
When current flowing through the E
C C.S
control
unit to drive the fuel pump IS too
small or too large while the engine
is operating.
6) Detonation sensor circuit (VG30ET engine)
When the circuit
is shorted with the engine
operating
at a speed of above 2,000 rpms
When the circuit is shorted or open
7) Fuel temperature sensor circuit
EF & EC-35

SELF-DIAGNOSIS
-Self-diagnostic System (Cont'd)-
CAUTION.
a. Always turn the diagnosis mode selector
carefully using
a screwdriver Do not press
hard to turn. Otherwise, the selector may be
damaged
b. When the engine fails to start, crank the engine
more
than two seconds before starting the
self-diagnosing.
c. Before starting the self-diagnosing, do not erase
the stored memory. Doing
so will reduce
the self-diagnosis function considerably.
d. After a malfunctioning area has been corrected,
be sure to erase the memory
e. The self-diagnosed results are retained in the
memory by a small current flow from the
battery. Disconnecting the battery cable
or
the E.C.C.S.'s 15-pin connector erases the
memory stored. Always perform the
self-
diagnosing regarding "intermittent" checks
before disconnecting.
The crank
angle sensor signal plays an impor-
tant role in the E.C.C.S. A malfunctioning
sensor
is sometimes accompanied by a display
which shows malfunctions in other signal
systems.
In such a case, always start with
checking the crank angle sensor.
f
EF & EC-36

SELF-DIAGNOSIS
Self-diagnostic Procedure
fully counterclockwise -,
SEF651B
Turn Ignition switch to "ON" Poslflon1
Check harness for battery
source (Refer to page
EF &
EC-59, 8) If battery is
0 K , replace control unit
unit stay "ON" (Bulb check)
Turn diagnosis mode selector fully clockwise
Write down the malfunction- unit are displaying code No. 23, No 24
(VG30ET) and No 31.
I
SEF653B
ing code
SEF654B
unit are displaying code No 31
OK
Start engine 41
Make sure that N G Write down the malfunction-
unit are displaying code No 14 (VG30ET)
and No. 31 ing code
OK1
EF & EC-37

ELECTRONIC CONTROL SYSTEM INSPECTION
@ Throttle valve switch (Code No. 23)
Check harness for continuity
OK 1
Check the throttle valve switch for continuity
between
@ and @
Continuitv should exin
SEF686B
0.K I
Check continuity between @, @$ and ground
(Insulation check)
SEF6888
+
Replace E C C.S control unit
rlG
Adjust idle switch
1) On VG30ET engine only, disconnect
A A C
valve harness connector
2) Hold engine speed as follows by manually
opening the throttle
valve
VG30E engine (Without turbocharger)
VG30ET engine (With turbocharger)
3) Adfust idle switch so that the switch
900+50 rpm
850*50 rpm
turns on at that engine speed
SEF687B
1) If idle switch cannot be adjusted, replace
5) Connect A A C valve harness connector
throttle valve switch
Replace throttle valve switch
EF 81 EC-50