Engine Controls - Theory & Operation - Eec: Other Ford Escort V рестайлинг

Due to Federal government requirements, manufacturers may use names and acronyms for systems and components different than those used in previous years. The following table will help eliminate confusion when dealing with these components and systems. Only relevant components and systems whose names have changed from current Ford Motor Co. terminology have been listed. See REVISED TERMINOLOGY table.

REVISED TERMINOLOGY

High Speed Inlet Air (HSIA) System (1.8L)

The HSIA system controls the length of intake air path to the intake manifold. The intake track is varied by opening and closing a shutter valve located inside the intake plenum. (Scheme 1) When engine speed is less than 5000 RPM, the HSIA solenoid directs vacuum to shutter valve to hold it closed. This shortens the intake air path.

When engine speed exceeds 5000 RPM, the HSIA solenoid vents vacuum to atmosphere, allowing shutter valve to open. This lengthens the intake air path. The vacuum reservoir ensures constant vacuum supply when manifold vacuum is low. The result is more engine torque in a wider range, at speeds less than 5000 RPM.

Scheme 1

Variable Resonance Induction System (VRIS) (2.5L)

VRIS opens and closes 3 shutter valves according to engine speed and throttle opening. VRIS shutter valves are located within the intake manifold. (Scheme 2) Two VRIS solenoids are operated by output signals from Powertrain Control Module (PCM). When solenoids are activated, vacuum is applied to the shutter valve actuators, which manipulate the shutter valves. Two vacuum chambers, located underneath left bank of intake manifold, maintain a constant vacuum supply to the VRIS shutter valves during Wide Open Throttle (WOT) and other low-vacuum, low-speed conditions. The result is improved fuel efficiency and engine torque.

Scheme 2

CONTROL UNIT

The Powertrain Control Module (PCM) is a computer, which receives data from numerous sensors, switches and relays. The PCM cali-brates information received and then generates output signals to control various relays, solenoids and actuators. The PCM has failure detection and self-diagnostic capability.

On 1.8L and 2.0L A/T, PCM is integrated with the Transaxle Control Module (TCM). On all models, PCM is located on the center console behind the kick panel.

Note. Components are grouped into 2 categories. The first category covers INPUT DEVICES, which control or produce voltage signals monitored by the control unit. The second category covers OUTPUT SIGNALS, which are components controlled by the control unit.

Barometric Pressure (BARO) Sensor

BARO measures barometric pressure of atmosphere. The PCM will adjust air/fuel ratio, A/C cutoff, idle speed, and purge control to compensate for changing pressure. On 1.8L and 2.5L, sensor is located inside the PCM and cannot be serviced separately.

Brake On/Off (BOO) Switch

BOO switch is mounted on the brake pedal. It signals deceleration to PCM for air/fuel ratio adjustment.

Clutch Pedal Position (CPP) Switch

CPP switch is mounted at top of clutch pedal. Input signal from CPP is used by the PCM.

Coolant Temperature Sensor

See ENGINE COOLANT TEMPERATURE (ECT) SENSOR.

Crankshaft Position (CKP) Sensor

The PCM uses CKP input to determine engine speed. On 1.8L, the CKP sensor is incorporated with the Cylinder Identification (CID) photo sensor, mounted inside the distributor. A slotted disc rotates with the distributor shaft, passing through the photo sensor. As the slots pass through the sensor, the PCM calculates crankshaft position and engine speed. This signal affects air/fuel ratio, ignition timing and emissions.

On 2.0L A/T, CKP sensor is located in the distributor. A 4-vane rotor is mounted to distributor shaft and spins at camshaft speed. As the rotor passes through a magnetic Hall Effect switch, the PCM calculates crankshaft position and engine speed. This signal affects air/fuel ratio, ignition timing and emissions.

On 2.5L, 2 CKP sensors are used. One sensor is located within the distributor and the second sensor is mounted below the crankshaft pul-ley. On the distributor mounted CKP sensor, a 6-vane rotor is mounted to distributor shaft and spins at camshaft speed. As the rotor passes through a magnetic Hall Effect switch, the PCM calculates crankshaft position.

On CKP sensor mounted below crankshaft pulley, the sensor signal is generated directly at the crankshaft pulley. This signal is used at higher vehicle speeds when timing belt does not accurately represent crankshaft position. Input signals from both CKP sensors are sent to the PCM and used for adjusting fuel injection timing, ignition timing and emission control.

Cooling Fan Engine Coolant Temperature (ECTF) Sensor

ECTF signals coolant temperature to PCM. On 2.0L A/T, sensor is threaded into a housing on right side of engine. On 2.5L, sensor is threaded into a coolant elbow on left side of engine. On all models, when coolant reaches a predetermined temperature, PCM sends an output signal to energize cooling fans.

Data Link Connector (DLC)

The Data Link Connector (DLC) is used to perform the Quick Test diagnostic procedure. The DLC is located behind battery. When the PCM STI terminal of the DLC is connected to ground, fault code output function is activated.

EGR Temperature (EGRT) Sensor

EGRT sensor monitors EGR valve temperature. As EGR flow increases, EGRT sensor temperature increases. As temperature increases, sensor resistance decreases. The PCM uses this signal to monitor EGR valve operation.

EGR Valve Position (EVP) Sensor

EVP sensor detects EGR valve position and transmits information to the PCM. Sensor is mounted on top of EGR valve. The EVP signal affects EGR flow and ignition timing.

Engine Coolant Temperature (ECT) Sensor

Sensor signals coolant temperature to PCM. The ECT sensor changes resistance in response to coolant temperature. The ECT sensor resistance decreases as coolant temperature increases. The PCM uses ECT sensor signal to adjust ignition timing, EGR flow (2.0L A/T and 2.5L), air/fuel ratio, idle speed and purge flow.

Heated Oxygen Sensor (HO2S)

HO2S monitors oxygen content of exhaust gases. This electrically heated O2 sensor is mounted in the exhaust manifold or pipe. When HO2S is at operating temperature, a voltage signal is produced, which varies according to oxygen content of exhaust gases. Signal is transmitted to the PCM, and is translated into a rich or lean mixture signal.

HO2S uses a built-in heating circuit. The heating circuit is used to bring the HO2S up to operating temperature, enabling faster conversion to closed-loop operation. The 2.5L is equipped with 2 sensors, one for each exhaust bank.

Idle Switch

The idle switch detects when throttle is closed and sends signal to PCM, indicating idle conditions are present. On 1.8L and 2.5L, idle switch is integrated into the throttle position sensor. On 2.0L A/T, idle switch is mounted on throttle body. On all models, PCM uses this signal to adjust air/fuel ratio and idle speed.

Intake Air Temperature (IAT) Sensor

On 1.8L and 2.5L, IAT sensor is mounted in the airflow meter. On 2.0L A/T, sensor is located in air filter housing. On all models, sensor monitors temperature of incoming air and then inputs signal to the PCM. The PCM uses this signal to adjust air/fuel ratio.

Knock Sensor (2.5L)

The knock sensor detects vibrations (pre-ignition) and converts them into a voltage signal. The PCM monitors signal from KS and adjusts ignition timing if pre-ignition occurs. The knock sensor is threaded into the engine block, near the oil pressure switch.

Manual Lever Position (MLP) Switch

On vehicles with A/T, the MLP switch monitors shift lever positions and then inputs signal to the PCM and Transaxle Control Module (TCM). This signal affects starter engagement, air/fuel ratio, idle speed and ignition timing.

Mass Airflow (MAF) Sensor

MAF sensor measures flow of air entering the engine. This measurement of airflow is proportional to engine load (throttle opening). The sensing element (hot wire) is a thin platinum wire wound on a ceramic bobbin and coated with glass. The hot wire is maintained at 392°F (200°C) hotter than the cold wire located downstream of hot wire. As air passes through airflow sensor, the air temperature is measured as it passes over the cold wire sensor. The PCM uses this information to calculate the required injector pulse width in order to provide desired air/fuel ratio.

Oxygen Sensor (O2S)

Voltage signal produced by the O2S indicates oxygen content of engine exhaust gases. O2S sensor is threaded into exhaust manifold. The PCM uses the O2S signal to regulate fuel injectors for proper air/fuel mixture.

Park/Neutral Position (PNP) Switch

The PNP switch, formally known as Neutral Drive Switch (NDS) or Neutral Gear Switch (NGS), is used on M/T models only. The PNP switch monitors in-gear conditions and then inputs signal to the PCM.

Power Steering Pressure (PSP) Switch

The PSP switch monitors power steering pressure. When power steering fluid pressure exceeds the preset limit, the PSP switch sends an input signal to the PCM. The PCM then adjusts idle speed. PSP switch is located in power steering pump.

Throttle Position (TP) Sensor

TP sensor monitors throttle plate opening. Its signal to PCM is proportional to opening angle. TP sensor is mounted on throttle body, at throttle plate shaft.

Transmission Oil Temperature (TOT) Sensor

TOT sensor is a thermistor that changes resistance as transmission fluid temperature changes. Sensor resistance decreases as fluid temperature increases. Sensor resistance variation is converted into a voltage signal and sent to PCM. PCM uses this input signal to determine transmission fluid temperature.

Volume Airflow Meter (VAF)

The VAF is mounted in the air inlet, between air cleaner and throttle body. It measures the volume of air entering into the engine by monitoring the position of a movable door. A potentiometer, attached to VAF door, signals door position to the PCM. The PCM translates door position to volume of air entering the engine.

The VAF also contains an air temperature sensor. The temperature of air entering the engine is monitored and transmitted to the PCM. The PCM is programmed to compute airflow and air temperature, so fuel flow can be adjusted to obtain optimum air/fuel mixture. The VAF also contains a fuel pump switching circuit to cut fuel pump operation when the engine is off.

Vehicle Speed Sensor (VSS)

Sensor is transaxle mounted. On 1.8L, the VSS turns a cable that is connected to the instrument cluster speedometer and transferred into a vehicle signal. On 2.0L A/T and 2.5L, VSS turns a Hall Effect sensor, which sends a constant pulse signal to PCM when vehicle is in motion.

OUTPUT SIGNALS

Note. Vehicles are equipped with different combinations of computer-controlled components. Not all components listed below are used on every vehicle. For theory and operation of each output component, refer to the system indicated after component.

A/C Relay

See MISCELLANEOUS CONTROLS.

Canister Purge (CANP) Solenoid Valve

See EVAPORATIVE EMISSION CONTROL under EMISSION SYSTEMS.

Cooling Fan

See MISCELLANEOUS CONTROLS.

EGR System

See EGR SYSTEM COMPONENTS under EMISSION SYSTEMS.

Fuel Injectors

See FUEL CONTROL under FUEL SYSTEM.

Fuel Pump Control

See FUEL DELIVERY under FUEL SYSTEM.

Fuel Pressure Regulator Control (FPRC) Solenoid

See FUEL DELIVERY under FUEL SYSTEM.

Idle Air Control (IAC) Valve

See IDLE SPEED under FUEL SYSTEM.

Idle Air Control/By-Pass Air (IAC/BPA) Valve

See IDLE SPEED under FUEL SYSTEM.

Malfunction Indicator Light

See SELF-DIAGNOSTIC SYSTEM.

FUEL SYSTEM

The fuel system is controlled by PCM, based on data received from EEC system. The PCM monitors engine operating conditions based on input received from engine switches and sensors. Control of output actuators determines fuel mixture and idle speed.

Fuel Pump

Fuel is supplied by in-tank electric fuel pump. Pump delivers fuel from fuel tank, through 20-micron fuel filter, to fuel charging manifold assembly. Fuel charging manifold assembly incorporates electrically actuated fuel injectors directly above each intake port. Injectors spray metered quantity of fuel into intake air. Constant fuel pressure is maintained to injector nozzles by pressure regulator.

Fuel Pump Relay

The Fuel Pump Relay (FPR) ground circuit is controlled by the PCM. The FPR is activated while engine is cranking and running.

Fuel Pressure Regulator

Fuel pressure regulator is attached to fuel supply manifold assembly downstream of fuel injectors. It regulates fuel pressure supplied to injectors. Regulator is controlled by a vacuum actuated diaphragm inside of regulator. Diaphragm vacuum is suppled by the Fuel Pressure Regulator Control (FPRC) solenoid.

FPRC solenoid valve is controlled by an output signal from the PCM. The FPRC solenoid controls vacuum to fuel pressure regulator. During hot starts, the FPRC solenoid prevents fuel percolation by stopping fuel pressure regulator vacuum supply. This allows fuel rail pressure to increase to full pressure.

Inertia Fuel Shutoff (IFS) Switch

In the event of a collision or vehicle rollover, electrical contacts within the inertia switch trip open and voltage supply to the electric fuel pump is shut off. If the electrical circuit trips, it is not possible to restart the vehicle unless the switch is reset. A reset button is located on the switch assembly. IFS switch is located in the trunk below left side of floor mat.

The electronic fuel injection system is a pulse time, PFI system. The PCM controls fuel injectors to meter fuel quantity into intake ports. The PCM receives inputs from engine sensors to compute fuel flow necessary to maintain air/fuel ratio throughout entire engine operational range. The injector ON time of the injector is the only controlled variable in fuel delivery system. The PCM controls the length of time each injector is on or energized.

Each cylinder has a solenoid-operated injector, which sprays fuel toward back of each intake valve. Fuel injector nozzles are solenoid-operated valves, which meter and atomize fuel delivered to engine. Each injector receives battery voltage through an ignition switch circuit. The PCM-controlled ground circuit is used to complete the circuit and energize (on time) the injector. The injector ON time controls the amount of fuel delivered.

Injector bodies consist of solenoid-actuated pintle and needle valve assembly. Injector flow orifice is fixed, and fuel pressure at injector tip is constant. Fuel flow to engine is regulated by how long solenoid is energized. This length of time is known as pulse width. Atomization spray is obtained by shape of pintle.

By-Pass Air (BPA) Valve (1.8L)

BPA valve, mounted on intake manifold, consists of a thermowax material that expands or contracts depending on engine coolant temperature that passes through the valve. When engine is cold, the BPA valve supplies by-pass air into the intake manifold to increase idle speed. The BPA valve closes as coolant temperature increases.

Idle Air Control (IAC) Solenoid (1.8L)

IAC solenoid is an electromechanical device controlled by the PCM. The IAC solenoid is mounted on the throttle body and allows air to by-pass the throttle plate. The amount of air allowed to by-pass the throttle plate is determined by PCM and controlled by a duty signal.

IAC/BPA valve controls idle speed by regulating throttle plate by-pass air. ISC/BPA valve consists of air by-pass and idle air control solenoid valves. Air by-pass valve functions during cold engine conditions, at temperatures less than 140°F (60°C). Idle air control solenoid valve functions in all temperatures.

The air by-pass valve is controlled by the engine coolant temperature. The idle air control solenoid valve is controlled by the PCM.

See INPUT DEVICES under COMPUTERIZED ENGINE CONTROLS.

See INPUT DEVICES under COMPUTERIZED ENGINE CONTROLS.

1.8L

The DI system (formally Electronic Spark Advance - ESA) uses an Ignition Control Module (ICM), Crankshaft Position (CKP) sensor and PCM to regulate ignition timing. Piston position and engine RPM are monitored by CKP and Cylinder Identification (CID) sensor.

The CKP creates 4 evenly spaced signal pulses as slots in the outer edge of the disc pass through it. These signals are used to control transistors in the ICM to break the primary circuit in the ignition coil. The CKP also supplies the PCM with information for engine RPM and injector timing.

The CID sensor creates one signal pulse per distributor revolution as the inner slot of the disc passes through. This signal is sent to the PCM to identify cylinder No. 1 TDC (compression stroke) for calculation of injection timing.

2.0L A/T

The DI system uses an Ignition Control Module (ICM), Crankshaft Position (CKP) sensor and the PCM to regulate ignition timing. The ICM and ignition coil are integral with the distributor. The CKP sensor detects crankshaft angle and cylinder No. 1 TDC (compression stroke) for calculating ignition timing, fuel injection timing and engine speed. The distributor operates by using a Hall Effect vane switch assembly, which causes the ignition coil to be switched on and off by the PCM and ICM.

2.5L

The DI system uses an Ignition Control Module (ICM), Cylinder Identification (CID) Sensor, 2 Crankshaft Position (CKP) sensors and the PCM to regulate ignition timing. The ICM and ignition coil are integral with the distributor. The CID sensor is mounted in the distributor and sends a signal to the PCM. Signal is used for detection of cylinder No. 1 TDC position.

The CKP1 sensor is mounted in the distributor and creates 6 evenly spaced signals for each distributor revolution. These signals are used during start-up, in a back-up condition if the CKP2 sensor should fail or when the PCM STI terminal of the data link connector is grounded.

The CKP2 sensor is mounted to front of engine block below the crankshaft pulley. The CKP2 sensor signal is sent to the PCM when the projections of the signal rotor pass by the CKP2 sensor. This signal is used to control fuel injection timing, ignition timing, Idle Air Control (IAC) operation and engine speed detection when the PCM STI terminal of the data link connector is not grounded (except during starting).

EGR Modulator (EGRM) Valve

EGRM valve uses vacuum supplied by the EGR Vacuum Regulator (EVR) solenoid to control the amount of backpressure vacuum applied to EGR valve. If vacuum from the EVR solenoid is not applied to the EGRM valve, ported vacuum will operate the EGR valve.

Vacuum Control Valves (VCV)

Temperature-operated vacuum switches have 2 or more ports. They use wax pellet or bimetallic material to either open or close vacuum ports when normal engine operating temperature is reached. Valves are mounted in some part of cooling system so that the base is immersed in coolant.

Vacuum Delay Valves

Valves are inserted in vacuum lines to provide gradual application or release of vacuum to engine or emission control devices. Valves may be 1-way or 2-way, depending on function and part of system affected.

Vacuum Reservoir

Vacuum reservoir stores vacuum to provide a consistent vacuum signal. It prevents rapid fluctuations or sudden drops in a vacuum signal, such as that seen during acceleration.

Vacuum Restrictor

This orifice-type flow restrictor is used in several emission calibrations to control flow rate and/or actuation timing of components and systems.

Vacuum Vent Valves

Valve controls induction of fresh air into system to prevent accumulation of fuel vapors, which could cause decay of vacuum diaphragms. Valve may be vent valve only, or a combination of vent and delay valve. Valves should always be mounted so ports point downward.

EGR SYSTEM COMPONENTS

Note. Exhaust Gas Recirculation (EGR) is not used on 1.8L engines.

Exhaust Gas Recirculation (EGR) Valve

The EGR valve recirculates a portion of the exhaust gas back into the engine to reduce the amount of nitrogen release during combustion and to reduce combustion temperature. The amount of exhaust gases that are released into the engine are proportional to engine load.

EGR Temperature (EGRT) Sensor (2.0L A/T California Only)

See INPUT DEVICES under COMPUTERIZED ENGINE CONTROLS.

EGR Vacuum Regulator (EVR) Solenoid

EVR solenoid controls the vacuum applied to the EGR Modulator (EGRM) valve. The EVR solenoid is controlled by the PCM. Based on a series of inputs received from other components, the PCM determines when to activate the EVR solenoid. When EVR solenoid is deactivated, vacuum is vented to atmosphere.

See INPUT DEVICES under COMPUTERIZED ENGINE CONTROLS.

EGR Vent (EGRV) & EGR Control (EGRC) Solenoids (2.5L)

EGRC solenoid regulates vacuum supply to EGR valve. The EGRV solenoid vents vacuum into the atmosphere in order to maintain EGR valve position. Both solenoids are controlled by output signals from the PCM.

The CANP solenoid valve controls the amount of vapors drawn from carbon canister into the intake plenum. The PCM uses various inputs from sensors to determine calibration of vapor transfer.

When signaled by the PCM, CANP solenoid opens the passage between the carbon canister and the intake plenum. When de-energized, vacuum line to the purge valve is vented to the atmosphere. Carbon canister is purged by drawing vapors into air cleaner.

Carbon Canister

Carbon canister storage is used for evaporative fuel control on all vehicles. The evaporative emission control system stores gasoline fumes from fuel tank in a carbon canister until fumes can be drawn into engine for burning during combustion process.

Fill Control/Vent System

Fill limiting is accomplished through configuration of fill neck and/or internal vent lines within fill neck and tank. Vent system is designed to permit air space in 10-12 percent of tank when tank is filled to capacity. Air space allows for thermal expansion of fuel and provides aid to in-tank vapor vent system.

Pressure/Vacuum Relief Fuel Cap

This system consists of a sealed filler cap with integral pressure/vacuum relief valve. Fuel system vacuum relief is provided after 1.0 in. Hg of vacuum; pressure relief is provided after 1.8 psi (.13 kg/cm 2 ). Under normal conditions, fill cap allows air to enter fuel tank as fuel is used, while preventing vapors from escaping.

Rollover Vent Valve

This valve releases excessive fuel tank pressure to atmosphere. If vehicle is rolled over, valve will prevent fuel tank drainage through evaporative hoses. Rollover vent valve is located on top of fuel tank.

Vapor Separator

The vapor separator allows vapor to vent to the carbon canister, while holding fluid in fuel tank. Vapors are routed through a single vapor line to carbon canister in engine compartment.

The vapor separator is located between fuel tank and evaporative lines to carbon canister. Venting fuel vapor prevents engine surging due to fuel enrichment and assists in hydrocarbon emission control.

POSITIVE CRANKCASE VENTILATION (PCV)

The PCV system uses intake manifold vacuum to eliminate blow-by vapors from crankcase. The mixture is then passed into the combustion chamber and burned. PCV valve provides control by metering flow of blow-by vapors according to manifold vacuum.

Under conditions where abnormal amounts of blow-by gases are produced (such as worn cylinders or rings), the system is designed to allow excess gases to flow back through crankcase vent hose and into air inlet for consumption during normal combustion.

MALFUNCTION INDICATOR LIGHT (MIL)

The MIL will illuminate when ignition switch is turned to the ON position (bulb check), or when systems related to the EEC system malfunction during normal engine operation. For additional information, see G - EEC TESTS W/ CODES article in the ENGINE PERFORMANCE Section.

MISCELLANEOUS CONTROLS

Note. Although not considered true engine performance-related systems, some controlled devices may affect driveability if they malfunction.

A/C CLUTCH CYCLING PRESSURE SWITCH

On models with manual A/C system, the A/C clutch cycling pressure switch is mounted on top of the receiver-drier. Based on refrigerant system pressure, a signal is sent to the PCM. The PCM uses this signal to maintain system pressure within the programmed range.

The A/C relay is controlled by an output signal from the PCM. The signal acts as a circuit on/off switch for the compressor magnetic clutch. The PCM will de-energize the A/C relay during Wide Open Throttle (WOT) conditions. This relay is sometimes referred to as a Wide Open Throttle Air Conditioning Cutoff (WAC) relay.

The PCM regulates operation of the electric cooling fan through the low fan and high fan control relays. Using information supplied by the A/C relay and Cooling Fan Engine Coolant Temperature (ECTF) sensor or Engine Coolant Temperature (ECT) sensor, the PCM controls cooling fan operation by grounding and ungrounding relay circuits.