Eec Iv Theory/operation Ford Tempo I

DESCRIPTION

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. See ECA LOCATION table for location of ECA module.

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 EEC-IV ignition system is controlled by the ECA through a Thick Film Integrated (TFI-IV) ignition module. Ignition timing (advance or retard) and dwell are controlled with this system to improve ignition system performance. The ignition coil is an "E-core" version and replaces the earlier oil filled coil.

Air/fuel mixture operation is accomplished by one of 3 different fuel injection systems depending on engine size and vehicle model. A Multi-Point Fuel Injection (MPFI) system, Central Fuel Injection (CFI) system or Sequential Electronic Fuel Injection (SEFI) system may be used. See FUEL INJECTION SYSTEM APPLICATION table.

Emission control components controlled by this system include EGR and canister purge. These systems are normally off, but are turned on when a mixture change signal allows operation of these units.

ECA LOCATION

FUEL INJECTION SYSTEM APPLICATIONS

ABBREVIATIONS

1. A/C: Air Conditioning
2. ACCS: A/C Cycling Switch
3. ACC: A/C Clutch Compressor
4. ACT: Air Charge Temperature sensor
5. ACV: Thermactor Air Control Valve
6. AXOD: Automatic Transaxle Overdrive
7. BOO: Brake On/Off switch
8. BP: Barometric Pressure sensor
9. CANP: Canister Purge solenoid
10. CCO: Converter Clutch Override
11. CFI: Central Fuel Injection
12. DVOM: Digital Volt/Ohm Meter (see VOM)
13. ECA: Electronic Control Assembly, processor, computer
14. ECT: Engine Coolant Temperature sensor
15. EDF: Electric Drive Fan relay assembly
16. EEC: Electronic Engine Control
17. EGO: Exhaust Gas Oxygen sensor (see HEGO)
18. EGR: Exhaust Gas Recirculation system
19. EGRC: EGR Control solenoid or system
20. EGRV: EGR Vent solenoid or system
21. EVP: EGR Position sensor
22. EVR: EGR Valve Regulator
23. FI: Fuel Injector or Fuel Injection
24. FP: Fuel Pump
25. FPM: Fuel Pump Monitor
26. FWD: Front Wheel Drive
27. GND or GRND: Ground
28. HEDF: High Speed Electro Drive Fan relay or circuit
29. HEGO: Heated EGO sensor
30. HEGOG: HEGO Ground circuit
31. HO: High Output
32. HSC: High Swirl Combustion, engine type
33. IGN: Ignition system or circuit
34. INJ: Injector or Injection
35. ISC: Idle Speed Control
36. ITS: Idle Tracking Switch
37. KAM: Keep Alive Memory
38. KAPWR: Keep Alive Power
39. KOEO: Key On Engine Off
40. KOER: Key On Engine Running
41. KS: Knock Sensor
42. L: Liter(s)
43. LOS: Limited Operation Strategy, computer function
44. LUS: Lock-Up Solenoid
45. MAF: Mass Air Flow sensor, meter or circuit
46. MAP: Manifold Absolute Pressure sensor
47. MA SEFI: Mass Air Sequential Fuel Injection system
48. MCU: Microprocessor Control Unit
49. MIL: Malfunction Indicator Light
50. MPFI: Multi Point Fuel Injection
51. NDS: Neutral Drive Switch
52. NGS: Neutral Gear Switch
53. NPS: Neutral Pressure Switch
54. OCC: Output Circuit Check
55. OHC: Overhead Camshaft, engine type
56. OSC: Output State Check
57. PFE: Pressure Feedback EGR sensor or circuit
58. PIP: Profile Ignition Pickup
59. PSPS: Power Steering Pressure Switch
60. PWR GND: Power Ground circuit
61. RWD: Rear Wheel Drive
62. SEFI: Sequential Fuel Injection (see MA SEFI)
63. SIG RTN: Signal Return circuit
64. SIL: Shift Indicator Light
65. SPOUT: Spark Output Signal, from ECA
66. SS 3/4-4/3: Shift Solenoid circuit
67. STAR: Self Test Automatic Readout, test equipment
68. STI: Self Test Input circuit
69. STO: Self Test Output circuit
70. TAB/TAD: Thermactor Air Bypass/Thermactor Air Diverter Tandem solenoid valves operated by separate circuits.
71. TFI: Thick Film Ignition system
72. TGS: Top Gear Switch (cancels SIL operation in top gear)
73. THS: Transmission Hydraulic Switch
74. TP or TPS: Throttle Position Sensor
75. TTS: Transmission Temperature Switch
76. VAF: Vane Air Flow sensor or circuit
77. VAT: Vane Air Temperature
78. VBATT: Vehicle Battery Voltage
79. VM: Vane Meter
80. VOM: Analog Volt/Ohm Meter (see DVOM)
81. VPWR: Vehicle Power supply voltage (regulated 10-14 volts)
82. VREF: Voltage Reference (ECA supplied reference voltage, 4-6 volts)
83. VSC: Vehicle Speed Control sensor or signal
84. VSS: Vehicle Speed Sensor or signal
85. WAC: WOT A/C Cut-off switch or circuit
86. WOT: Wide Open Throttle

The engine control system consists of the ECA, sensors, switches, and actuators. In order for the ECA to perform properly, 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 will then send out electrical signals to control air/fuel ratio, emission controls, idle speed and ignition timing. Individual component operation is as follows

A/C Compressor Clutch Signal

Whenever battery voltage is applied to A/C compressor clutch, a signal is sent to the ECA (Pin No. 10). The ECA uses this signal to increase engine idle speed to compensate for added load created by A/C compressor. Idle speed is controlled by the Idle Speed Control By-Pass Air (ISC-BPA) valve on all MPFI and SEFI engines. CFI engines use a DC powered Idle Speed Control (ISC) motor.

Air Charge Temperature (ACT) Sensor (All Engines Except 1.9L MPFI Engine)

The ACT sensor is threaded into cylinder runner of intake manifold or attached to air cleaner. It provides ECA with air/fuel mixture temperature information. The ECA uses this information to adjust fuel mixture, primarily during cold start enrichment periods.

Barometric Pressure (BP) Sensor (1.9 MPFI & 2.3L Turbo MPFI Engines)

Sensor is mounted on right inner fender and measures barometric pressure of atmospheric air. Variations in atmospheric pressure are converted to electrical signals and sent to ECA. The ECA uses this signal to adjust fuel mixture in relation to altitude change.

Brake On/Off (BOO) Switch (2.3L MPFI, 2.3L Turbo MPFI, 2.5L CFI, 3.0L MPFI, & 3.8L MPFI (FWD) Engines)

The brake on/off switch signals the ECA whenever brakes are applied.

Knock Sensor (KS) (2.3L MPFI, 2.3L Turbo MPFI, 3.0L MPFI Engines)

The knock sensor is a piezoelectric device designed to resonate at approximately the same frequency as engine knock. This unit senses and amplifies engine detonation (knock) and signals ECA to retard timing.

EEC Power Relay (1.9L CFI, 1.9L MPFI, 2.3L MPFI, 3.8L MPFI (RWD), & 5.0L SEFI Engines)

This relay is activated by ignition switch. Relay supplies battery voltage to ECA when ignition switch is in the "ON" position. Some relays incorporate a time delay of 5-10 seconds. A time delay EEC power relay is used on 1.9L CFI engines. All other models use a power relay without time delay feature.

Note. The 2.3L Turbo MPFI, 2.5L CFI, 3.0L MPFI, and 3.8L MPFI (FWD) engines use an Integrated Relay Controller Module (IRCM). The IRCM incorporates the EEC power relay. See ECA OUTPUT CONTROLLED ITEMS in this article.

EGR Valve Position (EVP) Sensor (2.3L OHC MPFI, 2.5L CFI, 5.0L SEFI Engines)

This sensor is located on top of EGR valve. It tells the ECA the position of the EGR valve.the position of the EGR valve.

Engine Coolant Temperature (ECT) Sensor

The ECT is mounted in the block or manifold to monitor engine coolant temperature. A signal is transmitted to the ECA, throughout the entire range of operating temperatures. In turn, the ECA adjusts air/fuel mixture, ignition timing, and EGR operation. On models equipped with electronic instrument cluster, ECT output is also used to control the coolant temperature indicator.

Idle Tracking Switch (ITS) (1.9L CFI & 2.5L CFI Engines)

The ITS is a mechanically operated switch held open by the throttle stop lever when throttle is closed. The ITS is an integral part of the ISC motor. A signal is transmitted to the ECA that the ISC motor plunger is touching throttle.

Manifold Absolute Pressure (MAP) Sensor

1.9L CFI, 2.3L OHC MPFI, 2.3L HSC MPFI, 2.5L CFI, 3.0L MPFI, 3.8L MPFI & 5.0L SEFI Engines only: MAP sensor measures absolute pressure of mixture in intake manifold and sends a proportional signal to the ECA. It is mounted on right inner fender for 5.0L engine and left inner fender for all others.

Neutral Drive Switch (NDS) & Neutral Gear Switch (NGS)

The NDS is used on auto. trans. equipped vehicles to adjust idle speed due to increased load of engaged transaxle/transmission. Vehicles equipped with manual transaxle/transmission use a NGS switch to notify the ECA when transaxle/transmission is in or out of gear.

Heated Oxygen (HEGO) Sensor

This sensor constantly monitors oxygen content of exhaust gases. A voltage signal is produced which varies according to oxygen content of exhaust gases.

This signal is transmitted to the ECA and is translated into a rich or lean mixture signal. The 5.0L SEFI engines use 2 oxygen sensors, one in each exhaust manifold.

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 windows and metal tabs, that rotate past a stator assembly (Hall Effect switch). Ignition distributor does not have any mechanical or vacuum advance.

Power Steering Pressure Switch (PSPS) (2.3L MPFI, 2.5 CFI, 3.0L MPFI & 3.8L MPFI (FWD) Engines)

The power steering pressure switch signals the ECA when power steering pressure exceeds 400-600 psi. On Sable and Taurus models, switch is located on power steering rack.

Pressure Feedback Electronic (PFE) EGR Valve (1.9L CFI, 2.3L HSC MPFI, 3.0L MPFI & 3.8L MPFI Engine)

The PFE exhaust gas recirculation valve is a conventional ported EGR valve with a backpressure sensing element attached to it. The valve is used in conjunction with the backpressure transducer, to inform ECA of EGR valve position.

The PFE transducer converts varying exhaust pressure signals into a proportional analog voltage, which is used by the ECA to regulate EGR flow.

Self-Test Input (STI)

Self-Test Input (STI) trigger is a wire (pigtail) near SELF-TEST connector. It is used to activate SELF-TEST. SELF-TEST procedures are built into EEC-IV control module so system can display service codes for diagnosis of intermittent problems.

Throttle Position (TP) Sensor

The rotary TP sensor is mounted on side of throttle body and connected directly to throttle shaft. The TP sensor senses throttle movement and position, and transmits an electrical signal to ECA. These signals are used to indicate wide open throttle, closed throttle, or normal cruise conditions.

Vane Airflow (VAF) Meter (1.9L MPFI & 2.3L Turbo MPFI Engines)

The airflow meter housing incorporates a sensor to measure air temperature and a movable vane potentiometer to measure airflow. It is mounted between the air cleaner and the throttle body. VAF information is transmitted to the ECA.

Mass Airflow (MAF) Sensor (5.0L MA/MPFI)

Measures airflow into engine. Used by the ECA to calculate injector pulse width for stoichiometric air/fuel ratio.

A/C Cooling Fan Controller & Wide Open Throttle A/C (WAC) Cut-Off

The A/C cooling fan controller is operated by ECA, coolant temperature switch and brake/stop light switch. Controller provides an output signal which controls operation of A/C compressor clutch and engine cooling fan.

The WAC circuit is energized by ECA when wide open throttle condition is detected. During wide open throttle, power to A/C compressor clutch is interrupted. The A/C remains off for about 3 seconds after returning to part throttle.

Canister Purge Solenoid (CANP) (All Except 2.3L OHC MPFI, 2.3L Turbo MPFI & 2.3L CFI Engines)

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 by ECA.

EGR Control (EGRC) Solenoid (2.3L OHC MPFI Engine)

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 (EGRSO) Solenoid (1.9L MPFI & 2.3L Turbo MPFI Engines)

The 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 valve. Solenoid switched vacuum is also supplied to canister purge valve.

EGR Vent (EGRV) Solenoid (2.3L OHC MPFI Engine)

Solenoid vents EGR control solenoid vacuum line. When vent solenoid is energized, control solenoid can open EGR valve.

EGR Vacuum Regulator (EVR) (All Except 1.9L MPFI, 2.3L OHC MPFI & 2.3L Turbo MPFI Engines)

Controlled by a signal from the ECA. Regulates the amount of vacuum to the EGR valve to control operation.

Fuel Injectors

On MPFI and SEFI engines, each cylinder has a solenoid-operated injector which sprays fuel toward back of each intake 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 CFI engines, one solenoid-operated injector is used in the throttle body. On the 3.8L CFI engine, 2 solenoid-operated injectors are used inside the throttle body.

On all fuel injected models, the ECA controls length of time each injector is open. The "open" time of injector governs amount of fuel delivered.

Fuel Pump Relay

Fuel pump relay and ignition is activated by ECA when the ignition switch is in the "ON" or "CRANK" positions. When ignition is turned on, the relay is activated to supply initial line pressure to system. The 2.3L Turbo MPFI, 2.5L CFI, 3.0L MPFI, and 3.8L MPFI (FWD) engines use an Integrated Relay Controller Module (IRCM). The IRCM incorporates the fuel pump relay.

Idle Speed Control (ISC) Motor (1.9L CFI & 2.5L CFI Engines)

This DC motor provides idle speed control according to signals from ECA. Idle speed motor also controls high cam RPM, anti-diesel shutoff, dashpot, and pre-positioning for next vehicle start up. The ISC includes an integral Idle Tracking Switch (ITS).

Idle Speed Control-Bypass Air All Except (1.9L CFI & 2.5L CFI Engines)

The throttle air by-pass valve is a solenoid-operated valve controlled by ECA. The valve allows air to by-pass around throttle plates to control cold engine fast idle, no-touch start, dashpot, overtemperature idle boost, and engine load idle correction.

Integrated Relay Controller Module (IRCM) (2.3L Turbo MPFI, 2.5L CFI, 3.0L MPFI & 3.8L MPFI FWD Engine)

The integrated relay controller module interacts with the ECA to provide control of the cooling fan, A/C compressor clutch, and fuel pump. The module incorporates the EEC power and fuel pump relays. On Sable and Taurus models, control module is located above radiator, on radiator support.

Self-Test Output (STO)

STO is a circuit in the ECA which transmits service codes, as timed pulses, to either a VOM or diagnostic tester hooked-up at SELF-TEST connector. These pulses are read as diagnostic codes.

Shift Indicator Light (SIL) (1.9L CFI, 1.9L MPFI, 2.3L HSC MPFI, 2.5L CFI, & 5.0L SEFI Engines)

Shift indicator light indicates to driver when to shift gears for optimum fuel economy. ECA activates light based on engine speed and manifold vacuum levels.

Spark Output (SPOUT)

The TFI ignition module is located on side of distributor. SPOUT information is transmitted from the distributor to the ECA. A SPOUT connector is located in the SPOUT wire from the TFI module. The ECA uses this information to control ignition timing and advance.

Thermactor Air By-Pass (TAB) Solenoid (5.0L SEFI Engine)

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 (5.0L SEFI Engine)

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.

DIAGNOSIS & TESTING

For diagnostic and testing procedures, see appropriate EEC-IV TESTING article under TESTING & DIAGNOSTICS.

See also:
• ECA LOCATION