Engine Controls - Basic Diagnostic Procedures: Other Infiniti M45 II

Compression

Note. Ensure battery is fully charged to obtain specified cranking speed.

Note. If cylinder compression in one or more cylinders is low, repeat inspection using a small amount of oil poured into each cylinder. If compression pressure increases, piston rings may be worn or damaged. If compression pressure does not increase, a valve may be sticking or seating improperly. If compression in any 2 adjacent cylinders is low and does not change after oil is added, cylinder head gasket may be leaking.

1. Start engine and warm to normal operating temperature. Turn ignition off. Release fuel pressure. See «FUEL SYSTEM»(ref-151802-S39076091332003010800000) . Remove all ignition coils.
2. On all models, remove all spark plugs. Depress accelerator pedal fully to hold throttle valve wide open. Use Compression Gauge Adapter (J45402) or suitable rubber tipped adapter that is less than.79" (20.0 mm) in diameter.
3. On all models, attach compression tester to cylinder No. 1. Crank engine at specified speed and record highest gauge indication. See «COMPRESSION SPECIFICATIONS»(ref-151802-S13294477782003010800000) table. Repeat measurement for each cylinder.

COMPRESSION SPECIFICATIONS (1)

Exhaust System Backpressure

Exhaust system can be checked with a vacuum gauge or a pressure gauge. Remove front HO2S sensor. Connect a 1-5 psi pressure gauge, and run engine at 2500 RPM. If exhaust system backpressure is greater than 2 psi, exhaust system or catalytic converter is plugged.

If a vacuum gauge is used, connect it to intake manifold vacuum. Observe vacuum gauge reading at idle. Open throttle part way (about 2500 RPM) and hold steady. If vacuum gauge slowly drops after stabilizing, exhaust system should be checked for a restriction.

FUEL SYSTEM

Basic diagnosis of fuel system should begin with determining fuel system pressure.

CHECKING FUEL PRESSURE

1. Release fuel pressure to zero. See «FUEL PRESSURE RELEASE»(ref-151802-S17369107142003010800000). Install the inline fuel quick disconnected fitting between fuel damper and injector tube. (Scheme 1), (Scheme 2), (Scheme 3) or (Scheme 4). Connect the fuel pressure test gauge (quick connector adapter hose) to the inline fuel quick disconnected fitting.
2. Turn ignition switch ON and check for fuel leakage. Start engine and check for fuel leakage. Record fuel pressure gauge reading. See «FUEL PRESSURE»(ref-151802-S13987032282003010800000) table.
3. If result is unsatisfactory, check the following, fuel hoses and fuel tubes for clogging, fuel filter for clogging, fuel pump, and fuel pressure regulator for clogging. If OK, replace fuel pressure regulator. If not OK, repair or replace components as necessary.

FUEL PRESSURE

Scheme 1

Scheme 2

Scheme 3

Scheme 4

With CONSULT-II

Start engine. Perform FUEL PRESSURE RELEASE in WORK SUPPORT mode with CONSULT-II. After engine stalls, crank 2 or 3 times to release all fuel pressure. Turn ignition off.

Without CONSULT-II

Remove fuel pump fuse. (Scheme 5), (Scheme 6), (Scheme 7), (Scheme 8) or (Scheme 9). Start engine and allow to run until engine stalls due to lack of fuel. Crank engine 2-3 more times to verify all pressure has dissipated.

Scheme 5

Scheme 6

Scheme 7

Scheme 8

Scheme 9

FUEL PUMP CONTROL CIRCUIT

For information on testing relays and fuel system components, see SYSTEM & COMPONENT TESTING article. For complete wiring circuit of electrical components on a specific model, see ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL article.

Spark

Remove each ignition coil, leaving harness connected. Connect a known good spark plug to ignition coil. Place end of Spark plug against a suitable ground. Crank engine and check for spark. If spark does not exist, check ignition coil, power transistor and circuits.

Camshaft Position Sensor

See SENSORS & SWITCHES in appropriate SYSTEM & COMPONENT TESTING article.

Crankshaft Position Sensor

See SENSORS & SWITCHES in appropriate SYSTEM & COMPONENT TESTING article.

Ignition Coil Power Source (I35, QX4 & Q45)

Turn ignition on. Use voltmeter to check voltage between appropriate terminals as shown in illustration. (Scheme 10), (Scheme 11) and (Scheme 12). Battery voltage should exist. If resistance is not as specified, replace ignition coil.

Scheme 10

Scheme 11

Scheme 12

Condenser (Q45)

Turn ignition off. Disconnect condenser harness connector F23 (Gray, 2-pin), located at rear of engine compartment. (Scheme 13) Measure resistance between condenser terminals. Resistance should be more than one megohm at 77°F (25°C). If resistance is as specified, condenser is okay. If resistance is not as specified, replace condenser.

Scheme 13

Ignition Coil Resistance

See IGNITIONS SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article.

IDLE SPEED & IGNITION TIMING

Ensure idle speed and ignition timing are set to specification. For adjustment procedures, see ON-VEHICLE ADJUSTMENTS article.

IDLE SPEED & CO LEVEL

IGNITION TIMING (Degrees BTDC @ Idle)

SUMMARY

If no faults were found while performing BASIC DIAGNOSTIC PROCEDURES , proceed to appropriate SELF-DIAGNOSTICS article. If no DTC is found performing self-diagnostics, proceed to TROUBLE SHOOTING - NO CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.