The principle of operation of the ignition system
The ignition system does not use a conventional distributor and coil. It uses the crankshaft position sensor output signals to the ECM. The ECM detects the electronic ignition timing and turns on the ignition coil.
This type of distributorless ignition system uses a distribution method "waste spark". Each cylinder is paired with the opposite cylinder (1-4 or 2-3). Ignition occurs simultaneously in the cylinder rising on the compression stroke and in the cylinder descending on the exhaust stroke. A cylinder in the exhaust stroke requires very little available energy to light the spark plug. The rest of the energy is supplied to the spark plug in the cylinder on the compression stroke.
These systems use the EST signal from the ECM to control ignition timing. The ECM uses the following information:
- Engine load (manifold pressure or vacuum).
- atmospheric (barometric) pressure.
- Engine temperature.
- Intake air temperature.
- crankshaft position.
- Engine speed (rpm)
Electronic ignition coil
The electronic ignition coil fires two spark plugs at the same time. The electronic ignition coil is not serviced and is replaced as a single unit.
Crankshaft position sensor
The direct ignition system uses an inductive crankshaft position sensor. This sensor extends through its mount by approximately 0.05 inch (1.3mm) to the crankshaft pulse sensor. The pulse sensor is a special wheel mounted on the crankshaft or crankshaft pulley, which has 58 slots, 57 of which are located at an interval of 6 degrees. The last slot is wider and serves to generate "clock pulse". As the crankshaft rotates, slots in the encoder change the encoder's magnetic field, creating an inductive pulse. The 58th slot long pulse displays a specific crankshaft orientation and allows the ECM to continuously determine the crankshaft orientation. The ECM uses this information to generate ignition timing and fuel injection pulses that it sends to the ignition coils and fuel injectors.
Camshaft position sensor
The camshaft position sensor sends a signal to the ECM. The ECM uses this signal as "synchronization pulse" to open the fuel injectors in the required sequence. The ECM uses the camshaft position sensor signal to determine the #1 piston position during the power stroke. This allows the ECM to calculate the correct sequential fuel injection mode. If the ECM detects an invalid camshaft position sensor signal while the engine is running, DTC P0341 will set. If the camshaft position sensor signal is lost while the engine is running, the fuel injection system will go into sequential injection mode based on the last pulse and the engine will continue to run. As long as the fault is present, the engine can be restarted. It will operate in the design sequential injection mode with a 1 in 6 chance of correct injector sequence.
The principle of operation of the idle speed controller
The operation of the idle air control is controlled by the main throttle body idle settings and the idle air control valve.
The ECM uses an idle air control valve to adjust the idle speed based on conditions. The ECM uses information from various inputs such as coolant temperature, manifold vacuum, etc. for efficient idle speed control.
The principle of operation of the fuel supply system
The function of the fuel metering system is to supply the right amount of fuel to the engine in different operating modes. Fuel is supplied to the engine by separate fuel injectors mounted in the intake manifold next to each cylinder.
The main sensors that control fuel supply are the manifold absolute pressure sensor, the control oxygen sensor (HO2S1) and diagnostic oxygen sensor (HO2S2).
The manifold absolute pressure sensor measures the vacuum in the intake manifold. When the fuel demand is high, the sensor reads a low vacuum, such as when the throttle is fully open. The ECM uses this information to richen the mixture, thus extending the injector run time and supplying the correct amount of fuel. When decelerating, the vacuum increases. The change in vacuum is sensed by the MAP sensor and read by the ECM, which then reduces injector run time due to reduced fuel demand.
HO2S sensors
The HOS2 sensor is located in the exhaust manifold. The HO2S sensor detects the amount of oxygen in the exhaust gases to the ECM, and the ECM changes the air/fuel ratio for the engine by controlling the fuel injectors. The best air/fuel ratio for reducing emissions is 14.7 to 1, which allows the catalytic converter to perform most efficiently. Because of the constant measurement and adjustment of the air/fuel ratio, the fuel injection system is called "closed loop".
The ECM uses the outputs of various sensors to determine how much fuel the engine needs. Fuel is supplied under various conditions called "modes".
Start mode
When the ignition is on, the ECM turns on the fuel pump relay for two seconds. The fuel pump increases fuel pressure. The ECM also checks the engine coolant temperature sensor (EATING) and throttle position sensor (TP) and determines the air/fuel ratio needed to start the engine. It is 1.5 to 1 at -97°F (-36°C) coolant temperature up to 14.7 to 1 at 201°F (94°С) coolant temperature. The ECM controls the amount of fuel delivered during start mode by varying the fuel injector on and off times. It's done "pulsation" fuel injectors for a very short time.
Free flow mode
If the engine is flooded with excess fuel, it can be purged by fully depressing the accelerator pedal. The ECM will shut off the fuel supply completely, eliminating all signals to the injectors. The ECM maintains this performance as long as the throttle remains wide open and the engine is running below about 400. If the throttle position drops below about 80 percent, the ECM will return to start mode.
Driving mode
The drive mode has two states called "open circuit" And "closed loop".
Open loop
If the engine has just started and its speed is above 400 rpm, the system goes into "open circuit". IN "open loop" The ECM ignores the signal from the HO2S and calculates the air/fuel ratio based on input from the engine coolant temperature sensor and the manifold absolute pressure sensor. The sensor stays in "closed loop" before the following conditions occur:
- The HO2S is producing an erratic output indicating that it is too hot to work properly.
- The temperature of the coolant temperature sensor is higher than the set value.
- A certain amount of time has passed since the engine was started.
Closed circuit
Special values for the above conditions vary from engine to engine and are stored in an electrically erasable programmable read-only memory (EEPROM). When these conditions are met, the system goes into the mode "closed loop". IN "closed loop" the ECM calculates the air/fuel ratio (nozzle operating time) based on the oxygen sensor signal. This allows the air/fuel ratio to remain very close to 14.7 to 1.
Acceleration mode
The ECM responds to rapid changes in throttle position and airflow and supplies additional fuel.
Braking mode
The ECM responds to changes in throttle position and airflow and reduces fuel. If braking is very fast, the ECM may turn off the fuel supply for a short time.
Battery voltage correction mode
If the battery voltage is low, the ECM can compensate for the weak spark supplied by the ignition module in the following ways:
- Increase the duration of the fuel injector pulse.
- Increase idle speed.
- Increasing the ignition delay time.
Fuel cut mode
When the ignition is off, the fuel injectors do not supply fuel. This prevents the engine from running when the ignition is off. Fuel is also not supplied in the absence of control pulses from the central power source. This prevents flooding.
The principle of operation of the gasoline vapor recovery system
The gasoline vapor recovery system uses a carbon filter accumulation method. This method allows fuel vapor to be directed from the fuel tank to the storage device (filter) activated carbon to trap fuel vapors when the car is not running. When the engine is running, fuel vapor is blown off the carbon cell by the intake air and used in the normal combustion process.
Gasoline vapors from the fuel tank are directed to the branch pipe marked TANK. These vapors are adsorbed by carbon. The carbon filter is purged by the ECM when the engine has been running for a certain amount of time. Air is fed into the carbon filter and mixed with the vapours. The mixture is then fed into the intake manifold.
The ECM applies ground to turn on the EVAP canister solenoid valve. This valve is pulse width controlled (PWM) and turns on and off several times a second. The EVAP canister system purge cycle varies according to the operating mode determined by air mass flow, fuel trim and intake air temperature.
Erratic idling, engine stall, poor handling can be caused by the following reasons:
- Defective EVAP canister purge solenoid valve.
- Damaged carbon filter.
- The hoses are cracked, damaged, or not connected to the correct fittings.
Gasoline vapor recovery adsorber
The EVAP adsorber is an toxicity control device containing activated carbon granules. The EVAP adsorber is used to retain fuel vapors from the fuel tank. When certain conditions are met, the ECM activates the EVAP canister purge solenoid valve, allowing fuel vapor to enter the engine cylinders and be burned there.
The principle of operation of the forced crankcase ventilation system
The positive crankcase ventilation system is used to make full use of crankcase vapors. The crankcase is supplied with fresh air from the air filter. Fresh air mixes with the leaking gas, which then enters the intake manifold through a vacuum hose.
Check hoses and clamps regularly. If necessary, replace crankcase ventilation components.
A clogged or closed PVC hose can cause the following conditions:
- Rough idle
- Engine stall or low idle
- Oil leaks
- Oil in the air filter
- Sludge in the engine
A leaky PVC hose can cause the following conditions:
- Rough idle
- Engine stop
- High idle speed
Coolant temperature sensor
Engine coolant temperature sensor (ECT) is a thermistor (resistor that changes resistance with temperature), installed in the engine coolant stream. Low coolant temperature causes high resistance (100,000 ohms at -40°F [-40°C]), and high temperature causes a decrease in resistance (70 ohms at 266°F [130°C]).
The ECM applies 5 volts to the engine coolant temperature sensor through a resistor in the ECM and senses the change in signal level. The signal level is high on a cold engine and low on a hot one. By measuring the change in signal level, the ECM can determine the coolant temperature. The coolant temperature affects most of the systems controlled by the ECM. A malfunction in the ECT sensor circuit can cause DTC P0117 or P0118 to set. It should be remembered that these DTCs indicate a malfunction in the ECT sensor circuit, thus the correct use of the table will either repair the wiring or replace the sensor.
Throttle position sensor
The throttle position sensor is a potentiometer connected to the throttle body shaft. The throttle position sensor circuit consists of a 5 volt power wire and a ground wire from the ECM. The ECM calculates the throttle position by monitoring the voltage on this signal line. The output signal of the throttle position sensor changes with the position of the accelerator pedal, changing the throttle opening angle. In the closed throttle position, the throttle position sensor output is low, about 0.5 volts. When the throttle is opened, the output increases and at wide open throttle the output is about 5 volts.
The ECM can determine fuel delivery based on the throttle opening angle (at the command of the driver). A broken or poorly connected throttle position sensor can cause intermittent fuel bursts from the injector and rough idle because the ECM assumes the throttle is moving. A problem in either throttle position sensor circuit should set a DTC P0121 or P0122. After the DTC sets, the ECM will override the throttle sensor default and the engine will return some power. DTC P0121 results in a high idle speed.
Diagnostic oxygen sensors
Three-way catalytic converters are used to control hydrocarbon emissions (NS), carbon monoxide and nitrogen oxides (NOx). The catalyst inside the neutralizers keeps the chemical reaction going. This reaction oxidizes the HC and CO present in the exhaust gases and converts them into harmless water vapor and carbon dioxide. The catalytic converter also reduces NOx by converting it to nitrogen. The ECM monitors this process using the HO2S1 and HO2S2 sensors. These sensors provide a signal that displays the amount of oxygen in the exhaust gases entering and leaving the three-way converter. This reflects the ability of the converter to effectively convert the exhaust gases. If the catalytic converter is operating efficiently, the HO2S1 signals will be more active than the HO2S2 signals. Converter efficiency sensors work in the same way as sensors that control fuel delivery. The main function of these sensors is to monitor catalyst efficiency, but they also play a limited role in fuel management. If the sensor output indicates a bias voltage higher or lower than 450 mV for an extended period of time, the ECM will change the fuel trim slightly to ensure that the fuel supply is correct to control the efficiency of the converter.
A problem with the HO2S1 sensor will set DTCs P0131 or P0132, depending on the special condition. A problem with the HO2S2 signal will set DTCs P0137, P0138, or P0140, depending on the special condition.
Malfunction in the electric heater of the diagnostic oxygen sensor (HO2S2) or in its power or ground wire will cause a lower oxygen sensor response. This can lead to incorrect results of the catalyst efficiency monitoring diagnostics.
Exhaust gas recirculation valve
The exhaust gas recirculation system is used on engines equipped with an automatic transmission to reduce NOx emissions (nitrogen oxides), caused by high combustion temperature. The EGR valve is controlled by the ECM. The EGR valve delivers a small amount of exhaust gases to the intake manifold to reduce the combustion temperature. The amount of exhaust gas recirculated is controlled by varying the backpressure in the vacuum and at the gas outlet. If too much exhaust gas is introduced, combustion does not occur. For this reason, very little exhaust gas is allowed to pass through this valve, especially at idle.
The EGR valve is usually open when:
- The engine has warmed up.
- Higher idle speed.
Results of incorrect operation
Excessive exhaust gas flow weakens combustion, causing the engine to run rough or stall. If the exhaust gas flow is too high at idle, in motion or on a cold engine, the following conditions may occur:
- Engine stops after cold start.
- The engine stops at idle after braking.
- The engine produces pops while driving.
- Rough idle.
If the EGR valve is left open all the time, the engine may not idle. Too little or too much exhaust flow allows the combustion temperature to rise too high during acceleration and load. This can cause the following conditions:
- detonation combustion (detonation)
- Engine overheating
- Toxicity test failure
Intake air temperature sensor
The intake air temperature sensor is a thermistor - a resistor that changes resistance depending on the temperature of the air entering the engine. Low temperature causes high resistance (4500 ohms at -40°F [-40°C]), and high temperature causes a decrease in resistance (70 ohms at 266°F [130°C]).
The ECM applies 5 volts to the intake air temperature sensor through a resistor in the ECM and measures the change in signal level to determine the intake air temperature. The signal level is high when the air in the manifold is cold and low when the air is hot. The ECM obtains information about the intake air temperature by measuring the voltage.
The intake air temperature sensor is also used to control ignition timing when the air in the manifold is cold.
A malfunction in the intake air temperature sensor circuit sets DTCs P0112 or P0113.
Throttle Actuator Control System (TAC)
Throttle Actuator Control System (TAC) used to improve emissions, fuel economy and improve overall handling characteristics. Throttle Actuator Control System (TAC) eliminates the mechanical connection between the accelerator pedal and the throttle. Throttle Actuator Control System (TAC) eliminates the need for an automatic cruise control system and an idle air control motor. The following is a list of components of the throttle actuator control system (TAC):
- The accelerator pedal assembly includes the following components:
- Accelerator pedal.
- Accelerator pedal position sensor (APP).
- Sensor 2 APP.
- The throttle body assembly includes the following components:
- Throttle angle sensor 1 (TP).
- Throttle Angle Sensor 2 (TP).
- Throttle actuator motor.
- Throttle valve.
- ECM controller.
The ECM monitors the driver's acceleration requirement using 2 APP sensors. The voltage range of the APP sensor 1 is approximately 0.7-4.5 volts, changing as the accelerator pedal moves from the initial pedal position to the full pedal position. The range of the APP sensor 2 is approximately 0.3-2.2 volts, changing as the accelerator pedal is moved from the initial position of the pedal to the position of the pedal fully depressed. The ECM processes this information along with other sensor inputs to command the throttle to a certain position.
The throttle valve is controlled by a DC motor called the throttle motor. The ECM can drive this engine forward or reverse by controlling battery voltage and/or ground on the 2 built-in drivers. Throttle held at home position 5.7°throttle position sensor (TPS) by means of a constant force return spring. When the throttle motor is not energized, this spring holds the throttle in its original position.
The ECM monitors the throttle angle using 2 TP sensors. TP sensor 1 voltage range varies from approximately 0.7 to 4.3 volts when the throttle moves from 0 percent to wide open throttle (WOT). TP sensor 2 voltage range varies from approximately 4.3 to 0.7 volts when the throttle moves from 0 percent to wide open throttle (WOT).
The ECM performs a diagnostic that checks the voltage levels of both APP sensors, both TP sensors, and the throttle actuator motor circuit. It also controls the return speed through the action of both return springs, which are housed inside the throttle body assembly. These diagnostics are performed on a different time scale based on whether the engine is running or stopped.
Each time the ignition is turned on, the ECM performs a quick throttle return spring test to verify that the throttle can return to the 7 percent home position from the 0 percent position. This is to ensure that the throttle can be returned to its original position in the event of a drive motor circuit failure.
Manifold absolute pressure sensor
Manifold absolute pressure sensor (IDA) measures changes in intake manifold pressure associated with changes in engine load and changes in engine speed. It converts them into an output signal.
A closed throttle valve coasting produces a relatively low manifold absolute pressure signal. Absolute pressure is the opposite of vacuum. When the manifold pressure is high, the vacuum is low. The manifold absolute pressure sensor is also used to measure barometric pressure. It is performed as part of the manifold absolute pressure sensor calculations. With the ignition on and engine off, the ECM reads manifold pressure as barometric pressure and adjusts the air/fuel ratio accordingly. Height compensation allows the system to maintain power at low toxicity levels. The barometric function is updated periodically while driving at a constant speed or at wide open throttle. In the event of a malfunction in the barometric part of the manifold absolute pressure sensor, the ECM sets the default value.
A malfunction in the manifold absolute pressure sensor circuit sets DTCs P0107 or P0108.
The following table shows the difference between absolute pressure and vacuum relative to the MAP sensor output, which is shown on the top row of both tables.
MAP
volt | 4.9 | 4.4 | 3.8 | 3.3 | 2.7 | 2.2 | 1.7 | 1.1 | 0.6 | 0.3 | 0.3 |
kPa | 100 | 90 | 80 | 70 | 60 | 50 | 40 | 30 | 20 | 10 | 0 |
in. Hg | 29.6 | 26.6 | 23.7 | 20,7 | 17.7 | 14.8 | 11.8 | 8,9 | 5.9 | 2.9 | 0 |
VACUUM
volt | 4.9 | 4.4 | 3.8 | 3.3 | 2.7 | 2.2 | 1.7 | 1.1 | 0.6 | 0.3 | 0.3 |
kPa | 0 | 10 | 20 | 30 | 40 | 50 | 60 | 70 | 80 | 90 | 100 |
in. Hg | 0 | 2.9 | 5.9 | 8,9 | 11.8 | 14.8 | 17..7 | 20,7 | 23.7 | 26.7 | 29.6 |
Electronic engine management controller (ECM)
The ECM, located inside the dashboard on the passenger side, is the control center for the fuel injection system. It constantly monitors information from various sensors and manages systems that affect the operation of the car. The ECM also performs system diagnostic functions. It can recognize problems in operation, alert the driver through the indicator lamp (Check Engine), as well as store a diagnostic code (s) malfunctions (to her), which identify problem areas and help with repairs.
There are no repairable parts in the ECM. Settings are stored in the ECM in programmable read-only memory (PROM).
The ECM supplies 5 or 12 volts to power the sensors or switches. This is done with resistors in the ECM that are so high that the test lamp does not come on when connected to the circuit. In some cases, a regular commercially available voltmeter will not give an accurate reading because their resistance is too low. You should use a 10 megohm digital voltmeter to get an accurate reading. The ECM controls output circuits such as the fuel injectors, idle air control valve, A/C clutch relay by driving the ground circuit through transistors or a device called "four lane driver".
Fuel burner
Multi-port fuel injection unit (MFI) - a device controlled by a solenoid valve from the ECM. It directs pressurized fuel to a separate cylinder. The ECM energizes the fuel injector or solenoid valve until the ball or needle valve is normally closed. This allows fuel to flow to the top of the injector, past the ball or needle valve, and through the recessed guide plate to the injector outlet.
The guide plate has six holes that control the flow of fuel and form a conical spray pattern of fine fuel at the nozzle nozzle. Fuel from the nozzle is directed to the intake valve, where it is atomized and evaporated further before being fed into the combustion chamber. A partially open fuel injector causes a drop in fuel pressure after the engine is stopped. Also, some engines have a longer start time. The operation of the engine with the ignition off can also be caused by the possibility of fuel supply.
Knock sensor
The knock sensor detects abnormal knocking in the engine. The sensor is mounted in the engine block next to the cylinders. The sensor outputs an AC signal that increases with the force of the detonation. This signal is sent to the ECM. The ECM controls ignition timing to reduce knocking.