Engine Controls - Adjustments: Other Nissan Altima U13

ENGINE MECHANICAL

Before performing any on-vehicle adjustments to fuel or ignition systems, ensure engine mechanical condition is okay.

VALVE CLEARANCE

Note. All engines, except GA16DE and KA24DE, are equipped with hydraulic lifters. No adjustments are required.

1. Warm engine to normal operating temperature. Remove valve cover and spark plugs. Rotate crankshaft to bring piston No. 1 to TDC on compression stroke (lifters on cylinder No. 1 should be loose).
2. Measure valve clearance on intake valves for cylinders No. 1 and 2 and valve clearance on exhaust valves for cylinders No. 1 and 3. See «VALVE CLEARANCE ADJUSTMENT»(ref-17440-S39354256882000122900000) table.
3. Rotate crankshaft 360 degrees to bring piston No. 4 to TDC on compression stroke. Measure valve clearance on intake valves for cylinders No. 3 and 4 and valve clearance on exhaust valves for cylinders No. 2 and 4. See «VALVE CLEARANCE ADJUSTMENT»(ref-17440-S39354256882000122900000) table. Adjust valve clearances by replacing lifter shims.

VALVE CLEARANCE ADJUSTMENT

4-CYLINDER IGNITION TIMING

1. Start engine and warm to normal operating temperature. Turn ignition off. Disconnect throttle position sensor harness connector.
2. Start engine. Increase engine speed to 2000 RPM, 2 or 3 times, then allow engine to return to idle. Engine should be operating smoothly at correct idle RPM. Check ignition timing. See 4-CYLINDER IGNITION TIMING table. (Scheme 6)
3. If ignition timing is incorrect, loosen hold-down bolt and turn distributor to adjust ignition timing. Turn ignition off and connect throttle position sensor harness connector. Recheck ignition timing.

4-CYLINDER IGNITION TIMING - (Degrees BTDC @ RPM)

Scheme 6

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 tests. For ECM connector terminal identification (Scheme 7)

4-CYLINDER IDLE MIXTURE

1. Start engine and warm to normal operating temperature. Increase engine speed to 2000 RPM for 2 minutes. Enter Mode II of vehicle's self-diagnostic system. See «TESTS W/CODES»(ref-17456) article.
2. Locate ECM. See ECM LOCATIONS table. Start engine. Raise engine speed to 2000 RPM. With idle speed and ignition timing set correctly, ensure Malfunction Indicator Light (MIL) and Red light on ECM goes on and off more than 5 times during a 10 second period.
3. If both lights operate as indicated, idle mixture is correctly set. If both lights do not operate as indicated, turn ignition off. Disconnect negative battery cable. Disconnect ECM and oxygen sensor wiring harness connector.
4. Using a jumper wire, connect oxygen sensor wiring harness connector terminal to ground. Check continuity between terminal No. 19 of ECM wiring harness connector and ground.
5. If continuity exists, remove jumper wire, reconnect ECM 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 between sensor wiring harness connector terminals. If vehicle is equipped with Pulse Air Injection System (PAIR), disconnect PAIR solenoid valve wiring harness connector. Connect negative battery cable.
7. Start engine and warm to normal operating temperature. Increase engine speed to 2000 RPM, 2 or 3 times. Check idle mixture (CO% level). See 4-CYLINDER IDLE SPEED & CO% LEVEL table under 4-CYLINDER IDLE SPEED. Remove 2500-ohm resistor from engine coolant temperature sensor wiring harness connector. Reconnect sensor.
8. If idle mixture (CO% level) is incorrect, go to next step. If idle mixture (CO% level) is correct, replace oxygen sensor. Start engine and increase engine speed to 2000 RPM. Ensure MIL on dash goes on and off more than 5 times during a 10 second period with engine running at 2000 RPM. If MIL does not perform as indicated, go to next step.
9. Reconnect oxygen sensor. Perform self-diagnostics. See «TESTS W/CODES»(ref-17456) article. If no fault codes are present, check fuel pressure, airflow meter, injectors and engine coolant temperature sensor for faults. If all systems are operating correctly but idle mixture is still incorrect, replace ECM.

ECM LOCATIONS

Scheme 7

THROTTLE POSITION (TP) SENSOR (4-CYLINDER ENGINES)

Note. Faults in TP sensor circuit may set Code 43. To test system, see CODE 43 diagnostic procedure in TESTS W/CODES article.

Turn ignition off. Ensure TP sensor wiring harness connector is securely connected. Adjust TP sensor by loosening mounting bolts and rotating sensor body until output voltage is within specification. See 4-CYLINDER TP SENSOR VOLTAGE table. (Scheme 8)

4-CYLINDER TP SENSOR VOLTAGE (1)

Scheme 8