Engine Mechanical - 2.5L: Diagnosis Nissan Altima L31

PRECAUTIONS FOR INSPECTION, REPAIR AND REPLACEMENT

1. Before repairing or replacing, thoroughly inspect parts. Inspect new replacement parts in the same way, and replace if necessary.

USE THE CHART BELOW TO HELP YOU FIND THE CAUSE OF THE SYMPTOM

1. Locate the area where noise occurs.
2. Confirm the type of noise.
3. Specify the operating condition of engine.
4. Check specified noise source.

If necessary, repair or replace these parts.

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Note. On vehicles not equipped with A/C, there is an idler pulley in the position for the drive belt routing.

1. Make sure that the stamp mark of auxiliary drive belt auto-tensioner is within the usable range. NOTE: Check the auto-tensioner indication when the engine is cold. When the new drive belt is installed, the range should be A. Visually check entire belt for wear, damage or cracks. If the indicator is out of allowable use range or belt is damaged, replace the belt.

Inspection After Installation

1. Check connections for fuel leakage.

1. Start the engine and run it for a few minutes with the engine at idle.
2. Stop the engine and check for fuel leakage both visually and by odor of gasoline. NOTE: Use mirrors for checking on connections out of the direct line of sight. CAUTION: Do not touch engine immediately after stopped as engine becomes extremely hot. Perform procedures for "Throttle Valve Closed Position Learning" after finishing repairs. Refer to «THROTTLE VALVE CLOSED POSITION LEARNING»(ref-135505-S20463220872002101400000) . If electric throttle control actuator is replaced, perform procedures for "Idle Air Volume Learning" after finishing repairs. Refer to «IDLE AIR VOLUME LEARNING»(ref-135505-S30377112672002101400000) .

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1. Remove engine under cover, with power tool.
2. Disconnect the electrical connector of each heated oxygen sensor, and unhook the harness from the bracket and middle clamp on the cover.
3. Remove the heated oxygen sensors with Tool. CAUTION: Be careful not to damage heated oxygen sensor. Discard any heated oxygen sensor which has been dropped from a height of more than 0.5 m (19.7 in) onto a hard surface such as a concrete floor; use a new one.
4. Remove the lower exhaust manifold cover.
5. Remove the exhaust front tube. Refer to «EXHAUST SYSTEM (QR25DE)»(ref-183496-S37820013822005081400000) .
6. Remove the upper exhaust manifold cover.
7. Loosen the nuts in the sequence shown, on the exhaust manifold and three way catalyst.
8. Remove the exhaust manifold and three way catalyst assembly and gasket. Discard the gasket.

Scheme 64

1. Use a reliable straightedge and feeler gauge to check the flatness of exhaust manifold fitting surface. Standard :0.3 mm (0.012 in)

Inspection After Removal

1. Clean the oil pickup screen to remove any foreign material.

1. Check for any engine oil leaks with the engine at operating temperature and running at idle.

Scheme 65

1. Use standard type spark plug for normal conditions. The hot type spark plug is suitable when fouling occurs with the standard type spark plug under conditions such as
2. frequent engine starts.
3. low ambient temperatures. The cold type spark plug is suitable when spark plug knock occurs with the standard type spark plug under conditions such as
4. extended highway driving.
5. frequent high engine revolution. Do not use a wire brush for cleaning the spark plugs. Replace as necessary. If plug is covered with carbon, a spark plug cleaner may be used. Cleaner air pressure :less than 588 kPa (6 kg/cm 2 , 85 psi) Cleaning time :less than 20 seconds Checking and adjusting plug gap is not required between change intervals. Gap :1.0 - 1.1 mm (0.0039 - 0.043 in)

Inspection

1. Perform this inspection as follows after removal, installation, or replacement of the camshaft or any valve-related parts, or if there are any unusual engine conditions due to changes in valve clearance over time (starting, idling, and/or noise).

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1. Warm up the engine, then stop it.
2. Remove front RH engine under cover using power tool.
3. Remove the rocker cover using power tool. Refer to «Removal and Installation»(ref-159291-S12621124542005042600000).
4. Turn crankshaft pulley in normal direction (clockwise when viewed from front) to align TDC identification mark (without paint mark) with timing indicator. see scheme 52
5. At this time, check that the both intake and exhaust cam noses of No. 1 cylinder face outside. If they do not face outside, turn crankshaft pulley once more.
6. By referring to the figure, measure valve clearances at locations marked X as shown in the table below (locations indicated with black arrow in figure) with a feeler gauge. No. 1 cylinder compression TDC. Use a feeler gauge, measure clearance between valve and camshaft. Valve clearance standard: Hot Intake:0.32 - 0.40 mm (0.013 - 0.016 in) Exhaust:0.33 - 0.41 mm (0.013 - 0.016 in) Cold* Intake:0.24 - 0.32 mm (0.009 - 0.013 in) Exhaust:0.26 - 0.34 mm (0.010 - 0.013 in) *Reference data at approximately 20°C (68°F) CAUTION: If inspection was carried out with cold engine, check that values with fully warmed up engine are still within specifications.
7. Turn crankshaft one complete revolution (360°) and align mark on crankshaft pulley with pointer.
8. By referring to the figure, measure valve clearances at locations marked X as shown in the table below (locations indicated with black arrow in figure). No. 4 cylinder compression TDC.
9. If out of specifications, adjust as follows.

1. Before starting engine, check the levels of engine coolant, lubricants, engine oil. If less than required quantity, fill to the specified level.
2. Run engine to check for unusual noise and vibration.
3. Warm up engine thoroughly to make sure there is no leakage of coolant, lubricants, oil, fuel, and exhaust gas.
4. Bleed air from passages in pipes and tubes of applicable lines.