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User Manual: D_ADJUST

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D - ADJUSTMENTS
1990 Nissan 240SX

1990 ENGINE PERFORMANCE
On-Vehicle Adjustments
Nissan; Axxess, Stanza, 240SX

ENGINE COMPRESSION
1) Start engine and warm to normal operating temperature.
Disconnect distributor center cable. Disconnect fusible link for
injectors. Check compression pressure with all spark plugs removed,
throttle valve wide open and engine at specified cranking speed.
2) Crank engine at least 6 revolutions to determine engine
compression. Compression reading should be within specification. See
ENGINE COMPRESSION table. After servicing engine, turn ignition off
and reconnect components disconnected. Erase memory Code 22 (if
necessary).
ENGINE COMPRESSION


Standard 
Minimum 
Minimum

Model

psi (kg/cm )

Axxess .......
Stanza .......
240SX ........

175 (12.3)
175 (12.3)
192 (13.5)

.....
.....
.....

psi (kg/cm )
146 (10.3)
146 (10.3)
142 (10.0)

RPM

.......
.......
.......

300
250
300


VALVE CLEARANCE

NOTE:

All engines except Z24i are equipped with hydraulic lifters.
No adjustment is required.

IGNITION TIMING
Axxess, Stanza, 240SX
1) Start engine and warm to normal operating temperature
(coolant gauge needle in middle). Open engine compartment hood and run
engine at 2000 RPM for 2 minutes. Perform self-diagnostic procedure.
See G - TESTS W/CODES article. Check for smooth engine operation.
2) Increase engine speed to 2000 RPM, 2 or 3 times, then
allow engine to return to idle. Check idle speed and ignition timing.
See 4-CYLINDER IGNITION TIMING table. See Fig. 1. If ignition timing
is correct, check idle mixture.
3) If ignition timing is incorrect, disconnect throttle
position sensor harness connector. If engine speed is more than 800
RPM, reduce idle speed with idle speed adjusting screw. See Fig. 2 or
3.
4) Recheck ignition timing. If timing is incorrect, loosen
hold-down bolt and turn distributor. With ignition timing correctly
set, reconnect throttle position sensor. Check idle speed, oxygen
sensor and idle mixture.

Fig. 1: Locating Ignition Timing Marks
Courtesy of Nissan Motor Co., U.S.A.
4-CYLINDER IGNITION TIMING (Degrees BTDC @ RPM)



Application
Axxess & Stanza ..........
240SX ....................

Man. Trans.
15 @ 650-750
15 @ 700-800

(1) Auto. Trans.
.............
.............

15 @ 650-750
15 @ 700-800

(1) - Auto. trans. in Neutral.


IDLE SPEED & MIXTURE

NOTE:

Mixture adjustment is NOT a normal tune-up procedure. DO NOT
adjust unless mixture control unit is replaced or vehicle
fails emissions test.

4-CYLINDER IDLE SPEED
Axxess, Stanza & 240SX

1) Start engine and warm to normal operating temperature.
Open engine compartment hood and run engine at 2000 RPM for 2 minutes.
Perform self-diagnostic procedure. See G - TESTS W/CODES article.
Check for smooth engine operation.
2) Increase engine speed to 2000 RPM, 2 or 3 times, then
allow engine to return to idle. Check idle speed. See 4-CYLINDER IDLE
SPEED & CO LEVEL table. If idle speed is correct, check ignition
timing and idle mixture.
3) If idle speed is incorrect, disconnect throttle sensor
harness connector. Ensure engine speed is less than 800 RPM (850 RPM
on Pickup). If idle is not as specified, adjust by turning idle speed
adjusting screw. See Fig. 2 or 3.
4) With idle speed set correctly, check ignition timing. If
timing is incorrect, loosen hold-down bolt and turn distributor. With
ignition timing correctly set, adjust idle speed to specification.
Reconnect throttle sensor and recheck idle speed using step 2).

Fig. 2: Adjusting Idle Speed (Axxess)
Courtesy of Nissan Motor Co., U.S.A.

Fig. 3: Adjusting Idle Speed (240SX)
Courtesy of Nissan Motor Co., U.S.A

4-CYLINDER IDLE MIXTURE
Axxess, 240SX
1) Start engine and warm to normal operating temperature.
Open engine compartment hood and run engine at 2000 RPM for 2 minutes.
Perform self-diagnostic procedure. See G - TESTS W/CODES article.
Check for smooth engine operation.
2) Check idle speed and ignition timing. With idle speed and
ignition timing correctly set, locate ECU under passenger’s seat
(behind center console, next to accelerator pedal on Axxess and
Stanza).
3) Increase engine speed to 2000 RPM for another 2 minutes.
If Green LED on ECU DOES NOT go on and off more than 5 times during 10
seconds with engine running at 2000 RPM, go to step 5).
4) If Green LED goes on and off more than 5 times during 10
seconds with engine running at 2000 RPM, enter and set self-diagnostic
system to Mode II. Red and Green LEDs on ECU should blink,
simultaneously. If both LEDs blink, idle mixture is correctly set. If
both LEDs do not blink simultaneously, go to step 7)
5) Turn off engine and disconnect negative battery cable.
Disconnect oxygen sensor and wiring harness from ECU. Using a jumper
wire, ground wiring harness at oxygen sensor connector.
6) Check continuity between terminal No. 19 of ECU wiring
harness connector and ground. If continuity exists, remove jumper
wire. Reconnect ECU and go to next step. If no continuity exists,
repair wiring harness. After repairs, reconnect negative battery
cable. Recheck idle speed and ignition timing.
7) Disconnect engine (coolant) temperature sensor. Connect a
2500-ohm resistor to engine (coolant) temperature sensor wiring

harness. Disconnect Air Induction Valve (AIV) and plug AIV pipe.
Reconnect negative battery cable.
8) Start engine and warm to normal operating temperature.
Increase engine speed to 2000 RPM, 2 or 3 times. Check idle mixture
(CO% level).
9) If idle mixture is correct, replace oxygen sensor. If
Green LED on ECU goes on and off more than 5 times during 10 seconds
with engine running at 2000 RPM, recheck idle speed and ignition
timing. If Green LED does not perform as indicated, go to next step.
10) If idle mixture is incorrect, reconnect oxygen sensor.
Perform self-diagnosis and repair procedures for fuel pressure,
airflow meter, injectors, and engine (coolant) temperature sensor. See
SELF-DIAGNOSTICS article.
11) After checking/adjusting idle mixture, turn off engine.
Remove 2500-ohm resistor from engine (coolant) temperature sensor
wiring harness and reconnect sensor. Reconnect AIV hose to pipe.
Stanza
1) Start engine and warm to normal operating temperature
(coolant gauge needle in middle). Open engine compartment hood and run
engine at 2000 RPM for 2 minutes.
2) Perform self-diagnostic procedure. See SELF-DIAGNOSTICS
article. Check for smooth engine operation. Check idle speed and
ignition timing. With idle speed and ignition timing set correctly,
locate ECU behind center console, next to accelerator pedal.
3) Increase engine speed to 2000 RPM for 2 minutes. Enter and
set self-diagnostic system in Mode II. See SELF-DIAGNOSTICS article.
Ensure Red LED on ECU goes on and off more than 5 times during 10
seconds with engine running at 2000 RPM.
4) If Red LED operates as indicated, idle mixture is
correctly set. If Red LED does not operate as indicated, turn off
engine and disconnect negative battery cable. Disconnect oxygen sensor
and wiring harness from ECU. Using a jumper wire, ground wiring
harness at oxygen sensor connector.
5) Check continuity between terminal No. 19 of ECU wiring
harness connector and ground. If continuity exists, remove jumper
wire. Reconnect ECU and go to next step. If continuity does not exist,
repair wiring harness. After repairs, reconnect negative battery
cable. Recheck idle speed and ignition timing.
6) Disconnect engine (coolant) temperature sensor. Connect a
2500-ohm resistor to engine (coolant) temperature sensor wiring
harness. Disconnect Air Induction Valve (AIV) and plug AIV pipe.
Reconnect negative battery cable.
7) Start engine and warm to normal operating temperature
(coolant gauge needle is in middle of gauge). Increase engine speed to
2000 RPM, 2 or 3 times. Check idle mixture (CO% level). See 4-CYLINDER
IDLE SPEED & CO LEVEL table.
8) If idle mixture is correct, replace oxygen sensor. Enter
and set self-diagnostic system in Mode II. If Red LED on ECU goes on
and off more than 5 times during 10 seconds with engine running at
2000 RPM, recheck idle speed and ignition timing. If Red LED does not
perform as indicated, go to next step.
9) If idle mixture is incorrect, reconnect oxygen sensor.
Perform self-diagnosis and repair procedures for fuel pressure,
airflow meter, injectors and engine (coolant) temperature sensor. See
G - TESTS W/CODES article.
10) After checking/adjusting idle mixture, turn off engine.
Remove 2500-ohm resistor from engine (coolant) temperature sensor
wiring harness and reconnect sensor. Reconnect AIV hose to pipe.
ECU GREEN LED FEEDBACK RESPONSE



Application

Flashes @ 2000 RPM

Axxess, 240SX ....................................................
Stanza (1) .......................................................

5
9

(1) - A single Red LED is used on these models.



4-CYLINDER IDLE SPEED & CO LEVEL


(1) Idle
RPM

Application
Axxess ..............
Stanza ..............
240SX ...............
(1)
(2)
(3)
(4)
(5)
(6)

-

(4) 650-750
(4) 650-750
(4) 700-800

(2) Idle
RPM
.
.
.

(4) 600-700
(4) 600-700
(4) 650-750

(3) CO
Level
........ (6) 5%
...... (6) 5.0%
...... (6) 5.0%

With throttle position sensor connected.
With throttle position sensor disconnected.
Measured in Self-Diagnostic Mode.
Auto. trans. in Neutral.
Idle speed is adjusted only with TPS connected.
Set CO level to less than 5 percent.


TPS CHECK & IDLE SWITCH ADJUSTMENT

NOTE:

Idle switch and throttle position sensor are contained in a
single assembly.

AXXESS (IDLE SWITCH)
1) Remove air duct and disconnect idle switch. Connect
ohmmeter between terminals "B" and "C". Ensure that continuity exists
with throttle valve fully closed (no continuity with throttle valve
open). If continuity is incorrect, replace idle switch.
2) To adjust idle switch, disconnect throttle position sensor
connector (idle switch connector plugged in). Install air duct. Locate
ECU behind center console, next to accelerator pedal. Start engine and
warm to normal operating temperature.
3) Enter and set self-diagnostic system to Mode IV. See G TESTS W/CODES article. Depress accelerator to 2000 RPM and release
slowly. Idle switch (Red LED on ECU) should turn on within the range
of 850-1150 RPM.
4) If idle switch does not come on as indicated, loosen holddown screws and turn TPS/idle switch body. After adjustment, turn
engine off. Remove air duct and tighten TPS/idle switch screws.
Reconnect throttle position sensor connector and install air duct.
Recheck idle switch on/off RPM.

STANZA (THROTTLE POSITION SENSOR)
1) Disconnect throttle position sensor. Connect ohmmeter
between terminals "E" and "F". See Fig. 4. Ensure resistance varies as
throttle is opened and closed. If resistance does not vary, replace
throttle position sensor.
2) Reconnect throttle position sensor. Start engine and warm
to normal operating temperature. Connect voltmeter between ECU
terminal No. 20 and ground. With ignition on, adjust TPS output
voltage to 0.4-0.5 volts. Disconnect TPS connector for few seconds,
then reconnect it. Turn ignition off.

240SX (TPS/IDLE SWITCH)

1) Disconnect throttle position sensor. Connect ohmmeter
between terminals "E" and "F". Ensure resistance varies as throttle is
opened and closed. If resistance does not vary, replace throttle
position sensor. Reconnect throttle position sensor.
2) Locate ECU on passenger’s side kick panel. Start engine
and warm to normal operating temperature. Turn self-diagnostic system
mode selector screw fully clockwise (Mode IV). See G - TESTS W/CODES
article.
3) Disconnect idle switch connector. Connect ohmmeter between
terminals "B" and "C". Check idle switch off/on speed, while closing
throttle valve. Idle switch should turn on at 850-1150 RPM. If idle
switch does not turn on, loosen idle switch hold-down screws and
rotate switch body to set off/on speed to specification.

Fig. 4: Identifying Idle Switch & TPS
Courtesy of Nissan Motor Co., U.S.A.



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