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

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

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

EVAPORATIVE EMISSION CONTROL SYSTEM
VAPOR VENT LINE
AN
Fuel check valve
SEC306A
1 Check hoses and fuel tank filler cap
2 Disconnect the vapor vent line connecting
carbon canister to fuel tank
3 Connect a 3-way connector, a manometer and
a cock (or an equivalent 3-way charge cock) to
the end of the vent line
4 Supply fresh air into the vapor vent line
through the cock
little by little untll pressure
becomes
3923 kPa (400 mmH,O, 1575
inH,
0)
5 Shut the cock completely and leave it un-
attended
6 After 25 minutes, measure the height of the
liquid
in the manometer
7. Variation in height should remain
at 0.245 kPa
(25 mmH,
0.0 98 inHl 0)
8 When filler cap does not close completely, the
height should drop to zero in
a short time
9 If the height does not drop to zero in a short
time when filler cap is removed, the cause IS a
stuffy hose.
In case the vent line is stuffy the breathing in fuel
tank
is not thoroughly made thus causing insuffi-
cient deliver of fuel to engine or vapor lock. It
must, therefore, be repaired or replaced.
tion.
CARBON CANISTER
Check carbon canister as follows
I-
UL
@ @)
inhale air and ensure that there IS no leakage inhale air and ensure that there 81 leakage
SEC307A
If malfunctioning, replace faulty part
FUEL TANK VACUUM RELIEF VALVE
1 Wipe clean valve housing and have it in your
mouth
2. Inhale air A slight resistance accompanied by
valve indicates that valve is in good mechanical
condition Note also that, by further inhaling
air, the resistance should be disappeared with
valve clicks
3. If valve is clogged, or if no resistance is felt,
replace cap
as an assembled unit
SEC308A
EF & EC-77