The basic ignition advance angle is determined using the NE signal and the VG signal or PIM signal. The NE and VG signal data used to determine the basic ignition advance angle is stored in the engine ECU memory.
1. Control when the IDL signal is ON
When the IDL signal is ON, the ignition timing is advanced in accordance with the engine speed.
HINT:
In some engine models the basic ignition advance angle is changed depending on whether or not the air conditioner is ON or OFF. In addition, of these models, some have an advance angle of 0 during standard idling speed.
2. Control when the IDL signal is OFF
The ignition timing is determined in accordance with the NE signal and VG or PIM signal based on the data stored in the engine ECU. Depending on the model, two basic ignition advance angles are stored in the engine ECU. The data for one of these is used to determine the advance angle based on the fuel octane value, so the data that matches the fuel used by the driver can be selected. In addition, some models of vehicles with fuel octane judgment capability use the KNK signal to automatically change the data used to determine the ignition timing.

The ESA (Electronic Spark Advance) system is a system that uses the engine ECU to determine the ignition timing based on the signals from the various sensors. The engine ECU calculates the ignition timing from the optimum ignition timing stored in memory to match the engine conditions, and then sends the ignition signal to the igniter. The optimum ignition timing is basically determined using.

The ESA system consists of the various sensors, engine ECU, igniters, ignition coil, and spark plugs.

Role of the sensors

Camshaft position sensor (G signal):

This detects the standard crank angle and the camshaft timing.

Crankshaft position sensor (NE signal):

This detects the crank angle and engine speed.

Air flow meter or manifold pressure

sensor (VG or PIM signal):

This detects the intake air mass or manifold pressure.

Throttle position sensor (IDL signal):

This detects the idling condition.

Water temperature sensor (THW

signal):

This detects the coolant temperature.

Knock sensor (KNK signal):

This detects knocking condition.

Oxygen sensor (OX signal):

This detects the oxygen concentration in the exhaust gas.

Role of the engine ECU

The engine ECU receives the signals from the sensors, calculates the optimum ignition timing for the engine conditions, and sends the ignition signal (IGT) to the igniter.

Role of the igniter

The igniter responds to the IGT signal output by the engine ECU to intermittently apply the primary current to the ignition coil. It also sends the ignition confirmation signal (IGF) to the engine ECU. engine speed and intake air mass (manifold pressure).

4. Acceleration enrichment
The air-fuel ratio becomes lean, especially during the start of acceleration because a fuel supply lag tends to occur during acceleration against the rapid change of the amount of the intake air when the accelerator pedal is depressed. For this reason, the injection duration is lengthened to increase the fuel injection volume against the intake air to prevent the air-fuel mixture from becoming lean. The acceleration is determined by the speed of the change in the throttle valve opening angle. The correction during acceleration increases greatly during the start of acceleration and is gradually reduced thereafter until the increase has ended. In addition, the more rapid the acceleration is, the larger the fuel injection volume increase.
5. Fuel cut-off
During deceleration, injection operation is stopped according to the deceleration condition in order to reduce the harmful exhaust gases and improve the engine braking effect. Then the fuel cut-off control is activated to cut-off the fuel injection. The state of deceleration is determined from the throttle valve opening and the engine speed. When the throttle valve is closed and the engine speed is high, it is determined that the vehicle is decelerating.
Fuel cut-off control
The fuel cut-off control stops the fuel injection when the engine speed is higher than a determined speed and the throttle valve is closed. Fuel injection will resume when the engine speed slows to a determined speed or the throttle valve is opened. The fuel cut-off engine speed and fuel injection resumption engine speed will increase when the coolant temperature is low. In addition, the fuel cut-off engine speed and fuel injection resumption engine speed are increased when the air conditioner switch is on to prevent the engine speed from falling and an engine from stalling. There are also some engine models in which these engine speeds drop during braking (i.e., when the stop light switch is on).
6. Power enrichment
As there is a large amount of the intake air at heavy loads, such as when climbing a steep hill, it is difficult to sufficiently mix the injected fuel with the intake air. And all of the intake air is not used during combustion, causing some to remain. Therefore, more fuel than for the theoretical air-fuel ratio is injected to use all of the intake air in combustion to increase power. Heavy loads are determined from the throttle position sensor opening, engine speed, and intake air mass (VG or PIM). The greater the intake air mass (VG or PIM) or the higher the engine speed is, the ratio of the increased amount becomes larger. In addition, the amount is further increased when the throttle valve opening angle becomes a certain value or more. The correction of the increased amount is from approx. 10% to 30%.
7. Intake air temperature correction
The air density changes depending on the air temperature. For this reason, a correction must be made to increase or decrease the fuel volume in accordance with the intake air temperature to optimize the mixture ratio required for the current engine conditions. The intake air temperature is detected by the intake air temperature sensor. The engine ECU is set to a standard intake air temperature of 20 C   (68 F). The correction amount is determined when the temperature rises above or falls below this temperature. When the intake air temperature is low, the amount is increased because the air density is high. When at high temperature, the amount is decreased because the air density is low. The correction of the increased/decreased amount is approx. 10%.
HINT:
For hot-wire type air flow meters, the air flow meter itself outputs a corrective signal for the intake air temperature. Therefore, intake air temperature correction is not required.
8. Voltage correction
There is a slight delay between the time where the engine ECU sends an injection signal to the injector, and the time when the injector actually injects the fuel. If there is a severe drop in battery voltage, then this delay will be longer. This means that the time the injector injects the fuel is shorter than the time calculated by the engine ECU. Therefore, the ratio of air becomes higher (in other words, leaner) than the mixture ratio required by the engine. For this reason, the engine ECU adjusts this by making the injector injection duration longer in accordance with the battery voltage drop.

1. Start enrichment
The basic injection duration cannot be calculated from the amount of the intake air because the engine speed is low and the changes in the amount of the intake air are large at starting. For this reason, the fuel injection duration at starting is determined from the coolant temperature. The coolant temperature is detected by the water temperature sensor. The lower the water temperature is the fuel vaporization becomes worse. Therefore, the air-fuel mixture is made richer by lengthening the injection duration. The engine ECU determines that the engine is being started when the engine speed is 40rpm or less. In addition, when the engine speed suddenly falls below 40rpm due to a sudden increase of the load on the engine, a hysteresis is used to prevent the engine ECU from determining that an engine that has already been started is being started again unless the engine speed falls below 20rpm.
SERVICE HINT:
When there is a malfunction with the water temperature sensor, it can be considered as the worse startability.
REFERENCE:
To improve startability while the engine was cold, the old type of EFI had a cold start injector and cold start time switch in addition to the regular injector to increase the fuel volume at starting.

2. Warm-up enrichment
The amount of the fuel injection is increased because the fuel vaporization is poor during the cold engine. When the coolant temperature is low, the fuel injection duration is increased to make the air-fuel mixture richer in order to attain the drivability during the cold engine. The maximum correction is twice as long as normal temperature.
SERVICE HINT:
When there is a malfunction with the water temperature sensor, it can be considered as poor drivability.

3. Air-fuel ratio feedback correction (For most models)
When there are no major fluctuations in the engine load or engine speed, such as when idling or driving at constant speed after warming up, fuel (air-fuel mixture close to the theoretical air-fuel ratio) is supplied based on the amount of the intake air. The following corrections are activated when driving at a constant speed after warming up.
(1) Feedback control using the oxygen sensor (Air-fuel ratio feedback control)The engine ECU determines the basic injection duration to achieve the theoretical air-fuel ratio. However, a slight deviation from the theoretical air-fuel ratio occurs in accordance with the actual engine conditions, changes over time, and other conditions. Therefore, an oxygen sensor detects the oxygen concentration in the exhaust gas to determine if the current fuel injection duration becomes the theoretical airfuel ratio against the amount of the intake air. If the engine ECU determines from signals of the oxygen sensor that the air-fuel ratio is richer than the theoretical air-fuel ratio, it shortens the injection duration to make the air-fuel mixture leaner. Conversely, if it determines that the air-fuel ratio is lean, it will lengthen the injection duration to make the air-fuel mixture richer. The feedback control operates to maintain the average air-fuel ratio at the theoretical air-fuel ratio by repeatedly performing minor corrections. (This is called a closed-loopoperation.)
In order to prevent overheating of the catalyst and assure
good engine operation, air -furl ratio feedback does not
occur under the following conditions (open-loop operation):
During engine starting
During after-start enrichment
During power enrichment
When the coolant temperature is below a determined level
When fuel cut-off occurs
When the lean signal continues longer than a determined
time The center point (a) changes during the feedback control such as time passes. In this case, the center point is forced to be returned to the center. If it is not, it will cause the out of the correction range of the feedback control. This is called air-fuel ratio learned control or long fuel trim.
(2) Feedback control using the air-fuel ratio sensor (A/F sensor):
The output voltage of the oxygen sensor changes rapidly around the theoretical air-fuel ratio as shown in the illustration (upper). The A/F sensor data which the engine ECU attains is displayed in the hand-held tester. (When the air-fuel ration is lean, the voltage is high. Conversely, the voltage is low when rich.) As a result, the detection precision of the air-fuel ratio has been improved. If the current air-fuel ratio changes from the theoretical air-fuel ratio as shown in the illustration (below), the engine ECU continuously corrects the air-fuel ratio using the oxygen sensor signal. For the A/F sensor, however, the engine ECU corrects instantly by determining the amount of change from the theoretical air-fuel ratio.
(3) CO emission control correction for vehicles without an oxygen sensor or A/F sensorFor vehicles without an oxygen sensor or A/F sensor, a variable resistor can be used to adjust the CO concentration (%) during idling. Turning the resistor to the R side makes the concentration richer, and turning it to the L side makes it leaner. For vehicles equipped with an oxygen sensor or A/F sensor, however, CO adjustment is not required during idling because these vehicles are automatically adjusted to the proper air-fuel ratio using the sensor signal.

The engine ECU changes the fuel injection volume by changing the injector injection duration. The actual fuel injection duration is determined by the following two items.
1. The basic injection duration is determined by the amount of the intake air and the engine speed.
2. The various corrective injection durations are determined by the signals from the various sensors. The injection duration that the engine ECU finally outputs into the injector is added various corrections to the basic injection duration. There are following corrections:
Start enrichment
Warm-up enrichment
Air-fuel ratio feedback correction (some models only)
Acceleration enrichment
Fuel cut-off
Power enrichment
Other corrections

1. Fuel filter
The fuel filter removes dirt and impurities from the fuel that is compressed by the fuel pump.
2. Fuel pump filter
The fuel pump filter removes dirt and impurities from the fuel before entering the fuel pump.
SERVICE HINT:
If a fuel filter becomes clogged, it will reduce the fuel pressure sent to the injector, causing difficulties with engine starting or poor drivability.
HINT:
Some fuel pumps are installed on the outside of the fuel tank.
In some models a union bolt or various types of quick connectors are used to connect the fuel line.
Fuel Pump Control
1. Basic operation
The fuel pump only operates when the engine is running. Even when the ignition switch is turned ON, if the engine is not running, the fuel pump will not operate.
(1) Ignition switch ON:
When the ignition switch is in the IG position, the EFI relay turns on.
(2) Ignition switch START:
When the engine cranks, a STA signal (starter signal) is sent to the engine ECU from the ST terminal of the ignition switch. When the STA signal is input into the engine ECU, the engine turns on the transistor and the circuit opening relay is turned on. Then, current is allowed to flow into the fuel pump in order to operate the fuel pump.
(3) Engine cranking/running
At the same time the engine is running, the engine ECU receives the NE signal from the crankshaft position sensor, continuing the transistor on to keep the fuel pump operating.
(4) If engine is stopped:
Even when the ignition switch is ON, if the engine is stopped, the NE signal will no longer be input into the engine ECU, so the engine ECU will turn off the transistor, which turns off the circuit opening relay, causing the fuel pump to stop.
SERVICE HINT:
DLC 1
There are some vehicles equipped with a DLC1 as shown at left. When +B terminal and FP terminal of the DLC1 are shorted using an SST with the ignition switch turned ON, the current will flow to the fuel pump without passing through the circuit opening relay to operate the fuel pump. In this way, the inspection of the fuel pressure or pump operation can be performed by forcing the fuel pump to operate.
2. Fuel pump speed control
This control reduce the fuel pump speed to decrease the pump wear and electrical power when much fuel is not required, such as when the engine is running at low speed. When the current flows into the fuel pump through the contact B of the fuel pump control relay and the resistor, the fuel pump operates at low speed. When the engine is cranking, when the engine is running at high speed, or at heavy loads, the engine ECU switches the contact of the fuel pump control relay into A in order to operate the fuel pump at high speed.
HINT:
ON-OFF control with speed control (by engine ECU and fuel pump ECU)
Some models control the fuel pump speed using the fuel pump ECU instead of the circuit opening relay, fuel pump control relay and resistor. In addition, this type of control also has a fuel pump system diagnostic function. When a malfunction is detected, a signal is sent from the fuel pump ECU to DI terminal of the engine ECU.
3. Fuel pump shut-off system
Some vehicles have a mechanism where the fuel pump control stops the fuel pump in the following conditions to maintain safety.
(1) When an airbag inflatesWhen the SRS driver’s, front passenger’s, or side airbag inflates, the fuel cut-off control stops the fuel pump. When the engine ECU detects an airbag inflation signal from the center airbag sensor assembly, the engine ECU turns off the circuit opening relay to stop the fuel pump operation. After the fuel cut-off control operates, the fuel cut-off control can be cancelled by turning the ignition switch OFF, causing the fuel pump to reoperate.
(2) When the vehicle crashes or rolls overWhen the vehicle crashes, the fuel pump inertia switch will turn off the fuel pump to minimize fuel leakage. The fuel pump inertia switch is located between the fuel pump ECU and the engine ECU. When the ball in the switch moves at a collision, the switch is separated from the contact to turn it OFF and stop the fuel pump operation. After this fuel cut-off operates, push the reset switch to the top to reset the fuel cut-off control, causing the fuel pump to reoperate.
GasolineEngineFuel Injection Methods and Injection Timing
The fuel injection methods are to inject the fuel independently in each cylinder or to simultaneously inject the fuel into all the cylinders. There are also various injection timings, such as injecting at a determined timing or injecting in accordance with the changes in the amount of the intake air or engine speed. The basic fuel injection method and injection timing are as follows. In addition, the larger the injection volume is, the start of the injection timing becomes faster.
1. Independent (Sequential)
Fuel is injected independently for each cylinder once for every two crankshaft rotations.
2. Groups
The fuel is injected for each group once for every two crankshaft rotations.
2 groups
3 groups
4 groups
3. Simultaneous
The fuel is simultaneously injected to the respective cylinders once for each rotation of the crankshaft. The amount of fuel required for combustion is injected over two injections.

The fuel is taken from the fuel tank by the fuel pump and sprayed under pressure by an injector. The fuel pressure in the fuel line must be regulated to maintain stable fuel injection by the pressure regulator and pulsation damper.

Main components

Fuel tank

Fuel pump assembly

Fuel pump

Fuel pump filter

Fuel filter

Pressure regulator

Delivery pipe

Injector

Pulsation damper

Fuel Pump and Pressure regulator

The fuel pump is installed in the fuel tank and is integrated with the fuel filter, pressure regulator, fuel sender gauge, etc. The pump impeller is turned by the motor to compress the fuel. The check valve closes when the fuel pump is stopped to maintain the pressure in the fuel line and make it easier to restart the engine. If there is no residual pressure, vapor lock can easily occur at high temperatures, making restarting difficult. The relief valve opens when the pressure on the outlet side becomes too high in order to prevent the fuel pressure from becoming too high.

The pressure regulator controls the fuel pressure to the injector at 324 kPa (3.3 kgf/cm2). (Values may differ depending on engine models) In addition, the pressure regulator maintains the residual pressure in the fuel line in the same way as the fuel pump check valve. There are two types of fuel regulation methods.

1. Type 1

This type controls the fuel pressure at a constant pressure. When the fuel pressure exceeds the force of the pressure regulator’s spring, the valve opens to return fuel to the fuel tank and regulate the pressure.

HINT:

The injection port of the injector is applied the vacuum by the manifold vacuum, which draws out the fuel. This vacuum is always changing depending on the engine conditions. Therefore, for this type the engine ECU calculates the fuel injection amount per injection duration in accordance with the changes in the intake manifold vacuum to ensure that the injector properly injects the fuel.

2. Type 2

This type is equipped with a delivery pipe that continually regulates the fuel pressure to keep the fuel pressure higher than a determined pressure from the manifold pressure. The basic operation is the same as type 1, but because the manifold vacuum is applied to the diaphragm’s upper chamber, the fuel pressure is controlled by changing the fuel pressure when the valve is opened in accordance with the manifold vacuum. The fuel is returned to the fuel tank via the fuel return pipe.

HINT:

The injection port of the injector is applied the vacuum by the manifold vacuum, which draws out the fuel. This vacuum is always changing depending on the engine conditions. Therefore, for this type the fuel pressure is continuously regulated in accordance with the intake manifold vacuum to keep the fuel pressure above a set pressure to maintain a set injection amount per injection duration.

Gasoline Engine Pulsation Damper

The pulsation damper uses a diaphragm to absorb a slight amount of fuel pressure pulsation generated by the fuel injection and the compression of the fuel pump.

SERVICE HINT:

The fuel pressure can be inspected easily by the screw of the pulsation damper.

HINT:

Some engine models do not have a pulsation damper.

Injector

The injector injects fuel into the intake ports of the cylinders in accordance with the signal from the engine ECU. The signals from the engine ECU cause current to flow in the solenoid coil, which causes the plunger to be pulled, opening the valve to inject the fuel. Because the plunger stroke does not change, the amount of the fuel injection is controlled at the time the current is flowed to the solenoid.

SERVICE HINT:

Handling of the O-ring:

The O-ring must not be reused.

When installing the O-ring, first coat it with new gasoline.

When installing the injector to the delivery pipe, be careful not to damage the O-ring.

With the injector installed in the delivery pipe, turn the indicator by hand. If it does not rotate smoothly, the Oring is damaged.

The EFI system uses various sensors to detect the engine condition and vehicle running condition. And the engine ECU calculates at the optimum fuel injection volume, and causes the injectors to inject the fuel. The figure shows the basic EFI configuration.
Engine ECU
This calculates the optimum fuel injection duration based on the signals from the sensors.
Air flow meter or manifold pressure sensor
This detects the intake air mass or manifold pressure.
Crankshaft position sensor
This detects the crank angle and engine speed.
Camshaft position sensor
This detects the standard crank angle and the camshaft timing.
Water temperature sensor
This detects the coolant temperature.
Throttle position sensor
This detects the throttle valve opening angle.
Oxygen sensor
This detects the oxygen concentration in the exhaust gas.
Types of EFI
There are two types of EFI system classified by the amount of the intake air detection method.
1. L-EFI (Air-flow control type)
This type uses an air flow meter to detect the amount of the air flowing in the intake manifold. There are two types of detection methodsOne directly measures the intake air mass, and one makes corrections based on the air volume.
2. D-EFI (Manifold pressure controlctype)
This type measures the pressure in the intake manifold to detect the amount of the intake air using the intake air density.

1.Precautions on handling

(1) The engine oil used for the engine equipped with the turbocharger is used for not only lubricating the engine but for lubricating and cooling the turbocharger. As the engine oil is exposed to the heat of the turbocharger, its temperature rises easily. For this reason, the engine oil and engine oil filter maintenance should be carried out faithfully. Otherwise it causes the turbocharger to damage. If the recommended engine oil is not used, it causes the bearings of turbocharger to be damaged. Therefore, be sure to use the recommended engine oil.

HINTRefer to the Owner’s Manual or Maintenance Schedule as the replacement intervals of the engine oil and oil filter vary by the model or condition under which the vehicle is used.

(2) Since the bearings are not sufficiently lubricated just after starting a cold engine, racing or sudden acceleration of the engine causes damage to the bearings.

(3) After the engine is placed under heavy loads, such as after high-speed driving or long distance driving, allow the vehicle to idle for a few minutes before shutting it off.

NOTICE

The turbocharger temperature does not rise too high while driving as the turbocharger is cooled by the oil and coolant. When the engine is stopped immediately after high-speed driving, etc., circulation of the oil and coolant stop. This causes the turbocharger to remain uncooled, leading to damage such as sticking. Thus, it is necessary to idle and cool the turbocharger.

2. Precautions on maintenance

(1) Do not start the engine with the air cleaner or air cleaner case removed. Otherwise it will allow foreign particles to enter causing damage to the compressor wheels and turbine.

(2) In the case that the turbocharger malfunctions and must be replace, first check the following items for the cause of the problem and remedy as necessary.

Engine oil level and quality

Conditions under which the turbocharger was used

Oil lines leading to the turbocharger

(3) When removing the turbocharger, plug the intake and exhaust ports and oil inlet to prevent dirt or other foreign materials from entering the system.

(4) When removing and reinstalling the turbocharger, do not drop it, bang it against anything, or grasp it by easily deformed parts, such as the actuator or rod.

(5) When replacing the turbocharger, check for the accumulation of carbon sludge in the oil pipes, and if necessary, clean out or replace the oil pipes, too.

(6) When replacing the turbocharger, put the oil into the turbocharger oil inlet and turn the compressor wheel by hand to spread oil on the bearings.

(7) When overhauling or replacing the engine, cut the fuel supply after reassembly and crank the engine for 3seconds to distribute oil throughout the engine. Then idle the engine for 6seconds.

The water-cooled type intercooler utilizes coolant to cool the intake air. Although it utilizes coolant, the intercooler has its independent cooling system, not introducing the coolant from the engine cooling system. It consists of the intercooler, electric water pump, subradiator, and intercooler computer. The illustration on the left shows the 3SGTE engine produced from 1989-1999.