General description
1. The Electronic Engine Control System (EEC - IV) consists of an on-board computer known as the Electronic Control Unit (ECU) and information sensors that read engine data and send data to the ECU. In turn, the ECU, based on the information received from the sensors and the program stored in the computer, sends out various signals (commands) to control the engine operation.
2. The ECA is the "brain" of the EEC-IV system and is located inside the instrument cluster (behind the glove compartment, above the recirculation pipe). It receives data from a number of sensors and other electronic components (switches, relays, etc.), based on the information it receives. The ECA produces output signals to control various relays, solenoids, and other actuators (see below). The ECA is designed specifically to optimize emissions, save fuel, and improve the handling of your vehicle.
Input sensors
3. Some engines are equipped with a knock sensor (see figure), which signals the ECA about the occurrence of detonation, prompting the system to change the ignition timing.
4. When battery voltage reaches the air conditioning compressor clutch, a signal about this is transmitted to the ECA, which perceives it as an additional load and increases the engine idle speed to compensate.
5. The intake air temperature (ACT) sensor, screwed into the intake manifold guide (see figure), provides the ECA with information on the temperature of the air-fuel mixture. The ECA uses this information to adjust fuel delivery and control delivery during cold starting.
6. The EGR valve position sensor (EVP), located on the EGR valve itself (see figure), provides information to the ECA about the position of the EGR valve.
7. The Engine Coolant Temperature (ECT) sensor, located near the water outlet assembly (see figure), records the temperature of the engine coolant. The ECT sends a constantly changing signal to the ECA, which affects the ECA system's control of the fuel mixture, ignition timing, and EGR operation.
8. The manifold absolute pressure (MAP) sensor, mounted on the firewall (see figure), measures the absolute value of the mixture pressure in the intake manifold and sends a signal to the ECA.
9. The oxygen sensor (EGO), screwed into the exhaust manifold (see figure), constantly records the oxygen content in the exhaust gases. A signal is sent to the ECA system depending on the difference in oxygen content in the exhaust gases and the surrounding atmosphere. The ECA calculates the ideal ratio for the current engine operating conditions.
10. The crankshaft position and speed sensor (PIP) is housed in the same housing as the distributor and informs the ECA of the crankshaft position and speed. The PIP unit consists of an anchor with four windows and four tongues, which rotates behind the stator unit (Hall sensor).
11. Throttle Position Sensor (TPS), mounted on the side of the throttle body (see figure) and directly connected to the throttle shaft, it detects the movement and position of the throttle and transmits a signal to the ECA.
12. The electronic converter of the EGR system pressure feed (PFE) converts the signal of the exhaust pressure value into a proportional voltage, which is processed by the EEC-IV processor. The EEC-IV processor uses the signal from the PFE converter to calculate the optimal flow through the EGR.
External devices
13. The ECA-controlled control relay module generates an external signal that controls the operation of the air conditioning compressor clutch, electric fan and fuel pump.
14. The case cleaning solenoid (CANP) is located in the recess of the left wing (see figure), upon receiving a signal from the ECA, it switches the vacuum in the manifold on and off, thereby activating the case cleaning valve. When the solenoid is connected, the vacuum opens the cleaning valve.
15. The solenoid that controls the EGR system is located in the right rear corner of the engine compartment, on command from the ECA it switches the vacuum in the manifold, thus affecting the EGR valve. When voltage is applied to the solenoid, the vacuum opens the EGR valve.
16. EGR Switch Solenoid - An electric vacuum valve located between the manifold vacuum source and the EGR valve. A controlled vacuum bleed is located between the solenoid and the EGR valve. This vacuum bleed is called the back pressure change transducer (BVT). These two devices optimize the operation of the EGR valve. The body purge valve is also equipped with a vacuum switch solenoid.
17. The EGR vent solenoid opens the vacuum line to the EGR control solenoid. When the vent solenoid is energized, the control solenoid opens the EGR valve.
18. The auxiliary air control solenoid, in accordance with signals from the ECA, regulates the fuel/air ratio at idle, normal engine operation and in transient conditions.
19. On pre-1990 four-cylinder vehicles, a single solenoid-controlled fuel injector is located on the throttle body. On V6 and four-cylinder vehicles since 1991, the injectors are located in the intake manifolds. The ECA controls the length of time each injector is open.
The injector "opening" time determines the amount of fuel supplied. Information regarding injector replacement is contained in Chapter 4.
20. The fuel pump relay is activated by the ECA system when the ignition switch is in the "on" position. When the key is turned to the "on" position, the relay provides the initial pressure level to the system chapter 4 contains information on checking and replacing the fuel pump.
21. The Idle Speed Control (ISC) motor (four-cylinder engines before 1990) varies the idle speed in accordance with signals from the ECA. Information regarding the replacement of the ISC is given in chapter 4.
22. TFI - IV ignition module, on most vehicles it is mounted on the base side of the distributor - fires the ignition coil. The ECA uses the signal from the crankshaft position and speed sensor to determine the position of the crankshaft. The ignition timing is determined by the ECA, after which a signal is sent to the module to activate the coil. Further information regarding the TFI - IV module can be found in the relevant section chapters 5.
23. Compressor shutdown circuit when the throttle is fully open. Disconnects the compressor from the engine when the throttle is fully open and turns it on when it is partially closed.
Examination
24. Since testing sensors and external devices requires specialized test equipment, diagnostics of the above-described elements is not within the scope of this publication.
Replacement of elements
Inlet Air Temperature Sensor (ACT)
25. Disconnect the wire from the negative terminal of the battery.
26. Locate the ACT sensor on the intake manifold (see Fig. 2.5).
27. Remove the electrical connector from the sensor.
28. Unscrew the sensor with a wrench.
29. Wrap the threads of the new sensor with Teflon tape to prevent leaks.
30. Perform installation in reverse order.
EGR Valve Position Sensor (EVP) - For 4 Cylinder Engine
31. Disconnect the wire from the negative battery terminal.
32. Locate the EVR sensor on the EGR valve (see Figure 2.6).
33. Pull out the sensor electrical connector.
34. Unscrew the three mounting bolts and disconnect the sensor.
35. Installation is carried out in reverse order.
Coolant Temperature Sensor (ECT)
36. Disconnect the wire from the negative terminal of the battery.
37. Locate the ECT sensor near the water outlet assembly (see Figure 2.7).
38. Pull out the sensor electrical connector.
39. Unscrew the sensor with a wrench.
40. Wrap the threads of the new sensor with Teflon tape to prevent leaks.
41. Installation is carried out in reverse order.
Manifold Absolute Pressure (MAP) Sensor
42. Disconnect the wire from the negative battery terminal.
43. Locate the MAP sensor on the fire partition (see Figure 2.8).
44. Pull out the sensor electrical connector.
45. Disconnect the vacuum line from the sensor.
46. Unscrew the two mounting bolts and remove the sensor.
47. Installation is carried out in reverse order.
Exhaust Gas Oxygen (EGO) Sensor
48. Disconnect the wire from the negative terminal of the battery
49. Raise the vehicle and support it securely on stands. Locate the EGO sensor on the exhaust manifold (4-cylinder engine) or on the catalytic converter tube (V6 engines) (see Figure 2.9).
50. Disconnect the sensor electrical connector.
51. Unscrew the sensor with a wrench.
52. Apply anti-seize compound to the threads of the new sensor to prevent it from "welding" to the manifold.
53. Installation is carried out in reverse order.
Throttle Position Switch Sensor (TPS)
54. Before replacing the TPS switch, thoroughly study the procedure (see chapter 4). Adjusting the installed switch requires specialized calibration equipment. A description of this procedure is beyond the scope of this publication.
Case clear solenoid
55. Disconnect the wire from the negative battery terminal.
56. Locate the housing purge solenoid on the left side of the engine compartment, near the left wheel well (see Fig. 2.14).
57. Pull out the solenoid electrical connector.
58. Label the vacuum hoses and connections, then disconnect the hoses.
59. Remove the solenoid.
60. Installation is carried out in reverse order.