2001 INFINITI QX4 Fuel

Fuel Injection TimingNBEC0014S07
SEF179U
Two types of systems are used.
Sequential Multiport Fuel Injection System
NBEC0014S0701Fuel is injected into each cylinder during each engine cycle according to the firing order. This system is used
when the engine is running.
Simultaneous Multiport Fuel Injection System
NBEC0014S0702Fuel is injected simultaneously into all six cylinders twice each engine cycle. In other words, pulse signals of
the same width are simultaneously transmitted from the ECM.
The six injectors will then receive the signals two times for each engine cycle.
This system is used when the engine is being started and/or if the fail-safe system (CPU) is operating.
Fuel Shut-offNBEC0014S08Fuel to each cylinder is cut off during deceleration or operation of the engine at excessively high speeds.
Electronic Ignition (EI) System
DESCRIPTIONNBEC0015Input/Output Signal ChartNBEC0015S01
Sensor Input Signal to ECMECM func-
tionActuator
Crankshaft position sensor (POS) Engine speed (POS signal)
Ignition
timing con-
trolPower transistor Crankshaft position sensor (REF) Engine speed (REF signal)
Camshaft position sensor (PHASE) Piston position
Mass air flow sensor Amount of intake air
Engine coolant temperature sensor Engine coolant temperature
Throttle position sensorThrottle position
Throttle valve idle position
Vehicle speed sensor Vehicle speed
Ignition switch Start signal
Knock sensor Engine knocking
Park/neutral position (PNP) switch Gear position
Battery Battery voltage
ENGINE AND EMISSION BASIC CONTROL SYSTEM DESCRIPTION
Multiport Fuel Injection (MFI) System (Cont'd)
EC-30

System DescriptionNBEC0015S02
SEF742M
The ignition timing is controlled by the ECM to maintain the best air-fuel ratio for every running condition of
the engine. The ignition timing data is stored in the ECM. This data forms the map shown.
The ECM receives information such as the injection pulse width and camshaft position sensor signal. Com-
puting this information, ignition signals are transmitted to the power transistor.
e.g., N: 1,800 rpm, Tp: 1.50 msec
A ÉBTDC
During the following conditions, the ignition timing is revised by the ECM according to the other data stored
in the ECM.
IAt starting
IDuring warm-up
IAt idle
IAt low battery voltage
IDuring acceleration
The knock sensor retard system is designed only for emergencies. The basic ignition timing is programmed
within the anti-knocking zone, if recommended fuel is used under dry conditions. The retard system does not
operate under normal driving conditions. If engine knocking occurs, the knock sensor monitors the condition.
The signal is transmitted to the ECM. The ECM retards the ignition timing to eliminate the knocking condition.
Air Conditioning Cut Control
DESCRIPTIONNBEC0016Input/Output Signal ChartNBEC0016S01
Sensor Input Signal to ECM ECM function Actuator
Air conditioner switch Air conditioner ªONº signal
Air conditioner
cut controlAir conditioner relay Throttle position sensor Throttle valve opening angle
Crankshaft position sensor (POS) Engine speed (POS signal)
Crankshaft position sensor (REF) Engine speed (REF signal)
Engine coolant temperature sensor Engine coolant temperature
Ignition switch Start signal
Vehicle speed sensor Vehicle speed
Refrigerant pressure sensor Refrigerant pressure
Power steering oil pressure switch Power steering operation
System DescriptionNBEC0016S02This system improves engine operation when the air conditioner is used.
Under the following conditions, the air conditioner is turned off.
IWhen the accelerator pedal is fully depressed.
IWhen cranking the engine.
IAt high engine speeds.
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ENGINE AND EMISSION BASIC CONTROL SYSTEM DESCRIPTION
Electronic Ignition (EI) System (Cont'd)
EC-31

IWhen the engine coolant temperature becomes excessively high.
IWhen operating power steering during low engine speed or low vehicle speed.
IWhen engine speed is excessively low.
IWhen refrigerant pressure is excessively low or high.
Fuel Cut Control (at no load & high engine
speed)
DESCRIPTIONNBEC0017Input/Output Signal ChartNBEC0017S01
Sensor Input Signal to ECMECM func-
tionActuator
Vehicle speed sensor Vehicle speed
Fuel cut
controlInjectors Park/neutral position (PNP) switch Neutral position
Throttle position sensor Throttle position
Engine coolant temperature sensor Engine coolant temperature
Crankshaft position sensor (POS) Engine speed (POS signal)
Crankshaft position sensor (REF) Engine speed (REF signal)
If the engine speed is above 1,800 rpm with no load (for example, in neutral and engine speed over 1,800
rpm) fuel will be cut off after some time. The exact time when the fuel is cut off varies based on engine speed.
Fuel cut will operate until the engine speed reaches 1,500 rpm, then fuel cut is cancelled.
NOTE:
This function is different from deceleration control listed under ªMultiport Fuel Injection (MFI) Systemº, EC-28.
Evaporative Emission System
DESCRIPTIONNBEC0018
SEF927U
The evaporative emission system is used to reduce hydrocarbons emitted into the atmosphere from the fuel
system. This reduction of hydrocarbons is accomplished by activated charcoals in the EVAP canister.
The fuel vapor in the sealed fuel tank is led into the EVAP canister which contains activated carbon and the
vapor is stored there when the engine is not operating or when refueling to the fuel tank.
The vapor in the EVAP canister is purged by the air through the purge line to the intake manifold when the
engine is operating. EVAP canister purge volume control solenoid valve is controlled by ECM. When the engine
ENGINE AND EMISSION BASIC CONTROL SYSTEM DESCRIPTION
Air Conditioning Cut Control (Cont'd)
EC-32

operates, the flow rate of vapor controlled by EVAP canister purge volume control solenoid valve is propor-
tionally regulated as the air flow increases.
EVAP canister purge volume control solenoid valve also shuts off the vapor purge line during decelerating and
idling.
SEF428T
INSPECTIONNBEC0019EVAP CanisterNBEC0019S01Check EVAP canister as follows:
1. Pinch the fresh air hose.
2. Blow air into portAand check that it flows freely out of portB.
SEF231SB
Tightening TorqueNBEC0019S02Tighten EVAP canister as shown in the figure.
Make sure new O-ring is installed properly between EVAP can-
ister and EVAP canister vent control valve.
SEF427N
SEF943S
Fuel Tank Vacuum Relief Valve (Built into fuel filler cap)NBEC0019S031. Wipe clean valve housing.
2. Check valve opening pressure and vacuum.
Pressure:
15.3 - 20.0 kPa (0.156 - 0.204 kg/cm
2, 2.22 - 2.90 psi)
Vacuum:
þ6.0 to þ3.3 kPa (þ0.061 to þ0.034 kg/cm
2, þ0.87 to
þ0.48 psi)
3. If out of specification, replace fuel filler cap as an assembly.
CAUTION:
Use only a genuine fuel filler cap as a replacement. If an incor-
rect fuel filler cap is used, the MIL may come on.
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ENGINE AND EMISSION BASIC CONTROL SYSTEM DESCRIPTION
Evaporative Emission System (Cont'd)
EC-33

Vacuum Cut Valve and Vacuum Cut Valve Bypass ValveNBEC0019S04Refer to EC-591.
Evaporative Emission (EVAP) Canister Purge Volume
Control Solenoid Valve
NBEC0019S05Refer to EC-367.
Fuel Tank Temperature SensorNBEC0019S06Refer to EC-309.
SEF462UA
Evap Service PortNBEC0019S07Positive pressure is delivered to the EVAP system through the
EVAP service port. If fuel vapor leakage in the EVAP system
occurs, use a leak detector to locate the leak.
SEF200U
PEF838U
PEF917U
How to Detect Fuel Vapor LeakageNBEC0019S08CAUTION:
INever use compressed air or a high pressure pump.
IDo not exceed 4.12 kPa (0.042 kg/cm
2, 0.6 psi) of pressure
in EVAP system.
NOTE:
IDo not start engine.
IImproper installation of EVAP service port adapter to the EVAP
service port may cause a leak.
With CONSULT-IINBEC0019S08011) Attach the EVAP service port adapter securely to the EVAP
service port.
2) Also attach the pressure pump and hose to the EVAP service
port adapter.
3) Turn ignition switch ªONº.
4) Select the ªEVAP SYSTEM CLOSEº of ªWORK SUPPORT
MODEº with CONSULT-II.
5) Touch ªSTARTº. A bar graph (Pressure indicating display) will
appear on the screen.
6) Apply positive pressure to the EVAP system until the pressure
indicator reaches the middle of the bar graph.
7) Remove EVAP service port adapter and hose with pressure
pump.
8) Locate the leak using a leak detector. Refer to ªEVAPORATIVE
EMISSION LINE DRAWINGº, EC-36.
ENGINE AND EMISSION BASIC CONTROL SYSTEM DESCRIPTION
Evaporative Emission System (Cont'd)
EC-34

SEF941Y
SEF214Y
Fuel Pressure ReleaseNBEC0023Before disconnecting fuel line, release fuel pressure from fuel
line to eliminate danger.
WITH CONSULT-IINBEC0023S011. Turn ignition switch ªONº.
2. Perform ªFUEL PRESSURE RELEASEº in ªWORK SUP-
PORTº mode with CONSULT-II.
3. Start engine.
4. After engine stalls, crank it two or three times to release all fuel
pressure.
5. Turn ignition switch ªOFFº.
SEF933Y
WITHOUT CONSULT-IINBEC0023S021. Remove fuel pump fuse located in fuse box.
2. Start engine.
3. After engine stalls, crank it two or three times to release all fuel
pressure.
4. Turn ignition switch ªOFFº.
5. Reinstall fuel pump fuse after servicing fuel system.
SEF327Z
Fuel Pressure CheckNBEC0024IWhen reconnecting fuel line, always use new clamps.
IMake sure that clamp screw does not contact adjacent
parts.
IUse a torque driver to tighten clamps.
IUse Pressure Gauge to check fuel pressure.
IDo not perform fuel pressure check with system operat-
ing. Fuel pressure gauge may indicate false readings.
1. Release fuel pressure to zero.
2. Disconnect fuel tube joint between fuel damper and injector
tube and set fuel pressure check adapter (J44321).
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BASIC SERVICE PROCEDURE
Fuel Pressure Release
EC-39

SEF328Z
3. Install pressure gauge to the fuel pressure check adapter as
shown in the figure.
4. Start engine and check for fuel leakage.
5. Read the indication of fuel pressure gauge.
At idling:
With vacuum hose connected
Approximately 235 kPa (2.4 kg/cm
2, 34 psi)
With vacuum hose disconnected
Approximately 294 kPa (3.0 kg/cm
2, 43 psi)
If results are unsatisfactory, perform Fuel Pressure Regulator
Check.
SEF329Z
Fuel Pressure Regulator CheckNBEC00251. Stop engine and disconnect fuel pressure regulator vacuum
hose from vacuum gallery.
2. Plug vacuum gallery with a blind cap.
3. Connect variable vacuum source to fuel pressure regulator.
SEF718BA
4. Start engine and read indication of fuel pressure gauge as
vacuum is changed.
Fuel pressure should decrease as vacuum increases. If results
are unsatisfactory, replace fuel pressure regulator.
BASIC SERVICE PROCEDURE
Fuel Pressure Check (Cont'd)
EC-40

SEF937Y
SEF703X
Injector
REMOVAL AND INSTALLATIONNBEC00261. Release fuel pressure to zero.
2. Remove intake manifold collector. Refer to EM-20, ªTIMING
CHAINº.
3. Remove fuel tube assemblies in numerical sequence as
shown in the figure at left.
4. Expand and remove clips securing fuel injectors.
5. Extract fuel injectors straight from fuel tubes.
IBe careful not to damage injector nozzles during removal.
IDo not bump or drop fuel injectors.
6. Carefully install O-rings, including the one used with the pres-
sure regulator.
ILubricate O-rings with a smear of engine oil.
IBe careful not to damage O-rings with service tools, fin-
ger nails or clips. Do not expand or twist O-rings.
IDiscard old clips; replace with new ones.
7. Position clips in grooves on fuel injectors.
IMake sure that protrusions of fuel injectors are aligned
with cutouts of clips after installation.
SEF938Y
8. Align protrusions of fuel tubes with those of fuel injectors.
Insert fuel injectors straight into fuel tubes.
9. After properly inserting fuel injectors, check to make sure that
fuel tube protrusions are engaged with those of fuel injectors,
and that flanges of fuel tubes are engaged with clips.
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BASIC SERVICE PROCEDURE
Injector
EC-41