DESCRIPTION
Note. Some early Calif. Continental, Cougar, Mark VII and Thunderbird models are equipped with EEC-III. Refer to appropriate FORD MOTOR CO. EEC-III article in this section for information on this system.
The center of the EEC-IV system is the Electronic Control Assembly (ECA). The ECA receives information from various sensors and switches. Based on information received and the operation program in the ECA's memory, the ECA generates output signals to control engine operation.
The calibration module for EEC-IV system is mounted inside the ECA. The ECA is located in the passenger compartment, in one of the following locations: under center console, under dash on left side of steering column, under passenger seat, or under dash behind right kick panel.
Air/fuel mixture, ignition, and emission control
The EEC-IV system controls 3 major areas of engine operation: Air/fuel mixture, ignition, and emission control. Additionally, the system can control A/C compressor clutch operation and idle speed. The system provides self-diagnostic capabilities.
The air/fuel mixture control is accomplished by an air flow controlled, multi-point, fuel injection system on 1.6L and 2.3L EFI models. Capri, LTD, Marquis and Mustang models with 2.3L OHC engine use a Carter YFA feedback carburetors. Tempo and Topaz models with 2.3L HSC engine use a Holley 6149 feedback carburetors. On models with 3.8L and 5.0L engines, air/fuel mixture is controlled by a throttle body fuel injection system.
The ignition system is controlled by the ECA through a Thick Film Ignition (TFI) module. Ignition timing (advance or retard) and dwell are controlled with this system to improve ignition system performance.
Emission control components controlled by this system include EGR and canister purge. These systems are normally off, but are turned on when the engine is ready to operate with the mixture change caused by EGR and canister purge operation.
SYSTEM OVERVIEW
The engine control system consists of the ECA, sensors and switches, and actuators. In order for the ECA to properly perform its function, it must be kept constantly informed of engine operating conditions.
It is the task of the engine sensors to supply the ECA, via electrical signals, with specific information required to determine engine operating conditions. The ECA can then send out electrical signals of its own to control air/fuel ratio, emission controls, idle speed and ignition timing. Individual component operation is as follows
A/C Compressor Clutch Signal
When battery voltage is applied to compressor clutch, a signal is sent to ECA. ECA uses signal to increase engine idle speed to compensate for added load created by A/C compressor. Idle speed is increased by using throttle air by-pass valve on 1.6L and 2.3L EFI models, throttle kicker solenoid on 2.3L HSC and 5.0L models and idle speed control motor on all other models.
Air Charge Temp. (ACT) Sensor (2.3L HSC, 3.8L & 5.0L Models)
The ACT is threaded into cylinder runner of intake manifold or attached to air cleaner. ACT provides ECA with air/fuel mixture temperature information. The ECA uses this information for correcting fuel flow and to control fuel flow during cold enrichment (cold starts).
Airflow Meter Assembly (1.6L & 2.3L EFI Models)
The airflow meter consists of 2 sensors in a single housing, mounted between air cleaner and throttle body assembly. An air flow sensor and an air temperature sensor are both exposed to intake airflow. The combined information from these sensors allows ECA to determine the mass and temperature of air entering engine.
Airflow Meter Installation 1.6L and 2.3L EFI and Turbo models. Scheme 1
Barometric Pressure Sensor
Sensor is mounted on right inner fender and measures barometric pressure of atmospheric air on 1.6L and 2.3L EFI models. Signals are converted to electrical signals and sent to ECA. ECA uses this signal to calculate correct fuel flow for altitude compensation.
EGR Valve Position Sensor (2.3L HSC, 3.8L & 5.0L Engines)
This sensor is located on the top of the EGR valve. It tells the ECA the position of the EGR valve.
Engine Coolant Temperature (ECT) Sensor
This sensor, threaded into heater supply tube, monitors engine coolant temperature. The ECA interprets this as either cold or normal operating temperature. This influences ECA control of fuel mixture enrichment, ignition timing, and EGR operation. On models equipped with electronic instrument cluster, ECT output is also used to control coolant temperature indicator lamp.
Idle Tracking Switch (ITS) (2.3L OHC & 3.8L Engines)
The ITS is a mechanically operated electric switch held open by throttle linkage when throttle is closed. When throttle stop lever is against switch, ITS is open. The ITS is integral with the idle speed control motor.
Key Power (Ignition Switch)
This is simply a test input for Quick Test using Key On-Engine Off Self-Test routine. These tests are to detect hard faults only, not intermittent problems.
Manifold Absolute Pressure (MAP) Sensor (2.3L HSC, 2.3L OHC, 3.8L & 5.0L Engines)
MAP sensor measures absolute pressure of mixture in intake manifold and sends a signal to ECA that is proportional to absolute pressure. It is mounted on right inner fender for 5.0L engine and left inner fender for all others.
Neutral (Start) Switch
Automatic transaxle 1.6L models use only a neutral start switch. Manual transaxle 1.6L models use a neutral switch. The carbureted 2.3L engines (OHC and HSC) use a Park/Neutral switch. Function of either circuit is the same. It indicates that the engine is loaded or unloaded, and ensures that the vehicle cannot be started in gear. ECA uses signal generated by these switches to maintain same idle speed regardless of engine load.
Oxygen Sensor
This sensor is threaded into exhaust manifold where it constantly monitors oxygen content of exhaust gases. A voltage signal is produced which varies according to difference in oxygen content between exhaust gases and surrounding atmosphere.
This signal is sent to the ECA which translates exhaust gas oxygen content to air/fuel ratio. It then alters air/fuel ratio to hold the ideal ratio for current engine operating conditions. The 3.8L engine uses 2 oxygen sensors, 1 in each exhaust manifold. The sensor on 2.3L Turbo models is a heated oxygen sensor.
Profile Ignition Pick-Up (PIP)
The PIP informs the ECA of crankshaft position and speed. PIP assembly is integral with distributor on all models. PIP has an armature with 4 windows and 4 metal tabs that rotate past a stator assembly (Hall-Effect switch). Ignition distributor does not have any mechanical or vacuum advance. Distributor is adjustable for resetting base timing if necessary.
Self-Test Input
Self-test input is a wire (pigtail) in self-test connector used to start the Quick Test. Self-test procedures are built into EEC-IV control module so system can display continuous self-test codes for diagnosis of intermittent problems.
Throttle Position Sensor (TPS)
The TPS is mounted on side of throttle body and connected directly to throttle shaft. The TPS senses throttle movement and position and transmits an electrical signal to the ECA. These signals keep the ECA informed of wide open throttle, closed throttle, or normal cruise conditions.
A/C & Fan Controller Module
A/C and Cooling Fan Controller Module is operated by ECA, coolant temperature switch and stop-lamp switch. Controller module provides an output signal which controls operation of A/C compressor clutch and engine cooling fan.
EEC Power Relay
This relay is activated by ignition switch. Relay supplies battery voltage to ECA when switch is on. Some power relays incorporate a time delay of 5-10 seconds. If time delay is used, a throttle control activator assembly is also used. Time delay is used on 2.3L OHC Capri, LTD, Marquis, and Mustang models and on all 3.8L engine models. All other models use a power relay without time delay feature.
Canister Purge Solenoid
This solenoid switches manifold vacuum to operate canister purge valve when a signal is received from ECA. Vacuum opens purge valve when solenoid is energized.
EGR Control Solenoid
Solenoid switches manifold vacuum to operate EGR valve on command from ECA. Vacuum opens the EGR valve when the solenoid is energized.
EGR Shut-Off Solenoid
EGR shut-off solenoid is an electrically-operated vacuum valve located between manifold vacuum source and EGR valve. A controlled vacuum bleed is located between solenoid and EGR valve. This vacuum bleed is a Backpressure Variable Transducer. These 2 devices operate EGR for optimum performance. Vacuum switched by solenoid is also supplied to canister purge valve.
EGR Vent Solenoid
Solenoid vents EGR control solenoid vacuum line. When vent solenoid is energized, control solenoid can open EGR valve.
Exhaust Heat Control Valve
This valve diverts hot exhaust manifold gases to intake manifold riser pad to heat incoming air/fuel mixture. The ECA monitors coolant temperature and engine load to control operation of this valve. This valve is used on all 3.8L engines and may be used on 5.0L engine.
Feedback Control Solenoid
Feedback control is accomplished by this solenoid which regulates idle, off idle and main system air/fuel ratios according to ECA signals. The 2.3L OHC solenoid is mounted on side of carburetor. The 2.3L HSC solenoid is mounted on the firewall and uses vacuum to control the air/fuel ratio.
Fuel Injectors
On 1.6L and 2.3L EFI models, each cylinder has a solenoid-operated injector which sprays fuel toward back of each inlet valve. Each injector is energized through ignition circuit and grounded through ECA to complete circuit. Injectors deliver 1/2 the amount of fuel required for an operating cycle each time they open (twice per cycle).
On 3.8L and 5.0L engines, 2 solenoid-operated injectors are used inside the throttle body. On all fuel injected models, ECA controls length of time each injector is open. The "open" time of injector governs amount of fuel delivered.
Fuel Pump Relay (Fuel Injected Models)
Fuel pump relay is activated by ECA with ignition switch in "ON" or "CRANK" positions. When ignition switch is turned to "ON" position, relay is activated to supply initial line pressure to system.
Idle Speed Control (ISC) Motor
This is a DC motor used to provide idle speed control according to signals from ECA.
Self-Test Output
Part of the self-test connector, service codes are transmitted through the output in the form of timed pulses. These pulses are read as diagnostic codes.
Shift Indicator Lamp
Used on 1.6L, 2.3L OHC and 2.3L HSC engines to indicate to driver when to shift gears for optimum fuel economy. ECA signals lamp to light according to information received on engine speed and manifold vacuum levels.
Thermactor Air By-Pass (TAB) Solenoid
Solenoid provides a vacuum signal to by-pass valve in response to ECA signals. The TAB valve then by-passes thermactor pump air to atmosphere.
Thermactor Air Diverter (TAD) Solenoid
Solenoid provides a vacuum signal to diverter valve in response to ECA signals. The TAD valve then diverts thermactor pump air to either exhaust manifold or catalytic converter.
TFI Module
The TFI module triggers ignition coil and determines dwell. Module is mounted on side of distributor. ECA uses signal from Profile Ignition Pick-Up to determine crankshaft position. Ignition timing is determined within ECA. ECA then signals TFI module when to fire coil.
Throttle Air By-Pass Valve (1.6L & 2.3L EFI Models)
Throttle Air By-Pass Valve is a solenoid-operated valve controlled by ECA. It operates a variable-area metering valve. Responding to commands from ECA, valve controls both cold and warm idle air flow. Valve causes air to by-pass throttle plate, thereby adjusting idle speed.
Throttle Kicker Solenoid
Two-port valve with an atmospheric vent. A vacuum diaphragm is used to maintain nominal idle speed on command from ECA.
Wide Open Throttle (WOT) A/C Cutout Switch
This switch is used on 1.6L EFI, 2.3L OHC and 5.0L engines. This switch is energized by ECA when WOT condition is detected. During WOT, the A/C compressor clutch is opened until the engine returns to a lower engine load level.