Engine Controls - Adjustments Nissan Pathfinder I

ENGINE COMPRESSION

1. Start engine and warm to normal operating temperature. On V6 engines, release fuel pressure by removing fuel pump fuse. Leave fuse out during compression check. Restart engine. After engine stalls, crank engine 2-3 times to completely release fuel pressure.
2. On all models, disconnect distributor center cable. On 4-cylinder engines, disconnect fusible link for injectors.
3. Check compression pressure with all spark plugs removed, throttle valve wide open and engine at specified cranking speed.
4. 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

VALVE CLEARANCE

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

4-CYL Ignition Timing - Pickup

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 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. (Scheme 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. (Scheme 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.

Scheme 1

4-CYLINDER IGNITION TIMING (Degrees BTDC @ RPM)

V6 Ignition Timing - Pathfinder & Pickup

1. Start engine and warm to normal operating temperature. Open engine compartment hood and run engine at 2000 RPM for 2 minutes.
2. Perform self-diagnostic procedure mode II. See TESTS W/CODES article. Check for smooth engine operation. Increase engine speed to 2000 RPM, 2 or 3 times, then allow engine to return to idle.
3. Check ignition timing. See V6 IGNITION TIMING table. (Scheme 2) If ignition timing is incorrect, loosen hold-down bolt and turn distributor. With ignition timing correctly set, check idle speed and mixture.

Scheme 2

V6 IGNITION TIMING (Degrees BTDC @ RPM)

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 - Pickup

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 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. (Scheme 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).

Scheme 3

4-Cylinder Idle Mixture - Pickup

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 SELF-DIAGNOSTICS 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 TESTS W/CODES 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.

ECU GREEN LED FEEDBACK RESPONSE

4-CYLINDER IDLE SPEED & CO LEVEL

V6 Idle Speed - Pathfinder & Pickup

1. Start engine and warm to normal operating temperature. Open engine compartment hood and run engine at 2000 RPM for 2 minutes.
2. Perform self-diagnostic procedure. See TESTS W/CODES article. Check for smooth engine operation. Check ignition timing. With ignition timing correctly set, locate ECU under passenger's seat.
3. Check idle speed (auto. trans. in Neutral). If idle speed is correct, go to step 5). If idle speed is incorrect, disconnect Auxiliary Air Control (AAC) valve harness connector.
4. Adjust idle speed by turning idle speed adjusting screw. (Scheme 4) Reconnect (AAC) valve harness connector. Recheck ignition timing and idle speed. With idle speed correctly set, go to next step.
5. Increase engine speed to 2000 RPM for another 2 minutes. Ensure Green LED on ECU goes on and off more than 5 times during 10 seconds with engine running at 2000 RPM. If not, check oxygen sensor and idle mixture.
6. If Green LED operates as stated, increase engine speed to 2000 RPM, 2 or 3 times. Allow engine to return to idle. Enter and set self-diagnostic system to Mode II. See TESTS W/CODES article. Red and Green LEDs on ECU should blink simultaneously. If so, idle speed and mixture are correctly set. If not, check oxygen sensor and idle mixture.

V6 IDLE SPEED & CO LEVEL

Scheme 4

Note. On V6 models, no provision for idle mixture adjustment is given.

V6 Idle Mixture - Pathfinder & Pickup

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 TESTS W/CODES article. Check for smooth engine operation.
2. Check engine idle speed and timing. With idle speed and timing correctly set, locate ECU under passenger's seat.
3. Increase engine speed to 2000 RPM for another 2 minutes. Ensure Green LED on ECU goes on and off more than 5 times during 10 seconds with engine running at 2000 RPM. If not, go to step 5).
4. If Green LED operates as stated, increase engine speed to 2000 RPM, 2 or 3 times. Allow engine to return to idle. Enter and set self-diagnostic system to Mode II. See TESTS W/CODES article. Red and Green LEDs on ECU should blink simultaneously. If so, idle mixture is correctly set. If not, go to step 10).
5. Turn off engine and disconnect negative battery cable. Disconnect oxygen sensor and wiring harness from ECU. Using a jumper wire, ground wiring harness (center terminal) at oxygen sensor connector.
6. Check continuity between terminal No. 19 of ECU wiring harness connector and ground. If no continuity exists, repair or replace wiring harness. Reconnect negative battery cable. Repeat idle speed, ignition timing, and idle mixture adjustment procedures.
7. If continuity exists, remove oxygen sensor jumper wire and reconnect ECU. Disconnect engine (coolant) temperature sensor connector. Connect a 2500-ohm resistor to engine (coolant) temperature sensor wiring harness. Reconnect negative battery cable.
8. Start engine and warm to normal operating temperature. Increase engine speed to 2000 RPM, 2 or 3 times, then allow engine to return to idle. Check idle mixture (CO% level).
9. If idle mixture is correct, replace oxygen sensor. Ensure Green LED on ECU goes on and off more than 5 times during 10 seconds with engine running at 2000 RPM. If so, recheck ignition timing and idle speed. If not, 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 TESTS W/CODES article.
11. After checking/adjusting idle mixture, turn off engine. Remove 2500-ohm resistor from engine (coolant) temperature sensor wiring harness and reconnect sensor.

Fast Idle Speed Adjustment - Pickup

1. Start engine and warm to normal operating temperature. Stop engine and remove air cleaner assembly. Make sure that cam follower lever roller faces top of fast idle cam. If necessary, turn adjusting screw until top of cam faces center of cam follower lever roller.
2. Measure clearance between roller and top of fast idle cam. On man. trans. equipped models, clearance should be .079-.102" (2.0-2.6 mm). If clearance is incorrect adjust clearance to .091" (2.3 mm), by turning screw attached to fast idle cam lever.
3. On auto. trans. equipped models, clearance should be .071-.094" (1.8-2.4 mm). If clearance is incorrect adjust clearance to .083" (2.1 mm), by turning screw attached to fast idle cam lever.
4. On throttle bodies produced after January 1990, an alignment mark will be added to the fast idle cam. Set alignment mark to that it points to center of cam follower lever roller.

TPS CHECK & IDLE SWITCH ADJUSTMENT

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

4-Cylinder Engines - Pickup (Throttle Position Sensor)

1. Disconnect throttle position sensor. Connect ohmmeter between terminals "E" and "F". (Scheme 5) 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 0.4-0.6 volts. Disconnect TPS for few seconds, then reconnect. Turn ignition off.

Scheme 5

V6 Engines - Pathfinder & Pickup (TPS/Idle Switch)

1. Disconnect throttle position sensor. Connect ohmmeter between terminals "E" and "F". With throttle valve closed resistance should be 1000 ohms (9000 ohms fully open). If resistance is not as specified, replace TPS.
2. Start engine and warm to normal operating temperature. Disconnect Auxiliary Air Control (AAC) valve sub-harness connector. Disconnect idle switch.
3. Connect ohmmeter between terminals "A" and "B". Check idle switch off/on speed while closing throttle valve. Idle switch should turn on at 800-1100 RPM. If idle switch does not perform as indicated, loosen idle switch hold-down screws and rotate switch body to set off/on speed to specification.