Contents: Adjusting the engine speed and fuel…⤓ Checking the idle speed increase…⤓ Replacing and adjusting the idle…⤓ Adjusting the idle speed increase…⤓ Checking the idle speed control…⤓ Checking the braking, enrichment,…⤓ Checking and adjusting the throttle…⤓ Checking the air damper ⤓ Checking and adjusting the high idle…⤓ Checking the bimetallic air damper…⤓
Note: If your vehicle is hard to start or does not start at all, idles poorly, or drivability is poor and you suspect a carburetor problem, it is best to first take your vehicle to a professional who has the feedback carburetor testing equipment necessary to test such a complex system. The following procedures are intended to assist the non-technical mechanic in determining component functionality, making minor adjustments, and replacing some components. These procedures are not intended to correct any problems.
Adjusting the engine speed and fuel mixture composition at idle
1. Adjustment of the idle speed is described in Chapter 1. Adjusting the fuel mixture composition cannot be done independently, since it requires an exhaust gas analyzer. This work must be done by specialists.
Checking the idle speed increase system when turning on the electrical devices and power steering
2. Check the vacuum hoses and the ISR solenoid wiring to ensure proper connection (see illustration).
11.2a. Check the idle speed increase drive hose (1) for cracks and aging - disconnect the hose from the vacuum fitting before checking the drive; to remove the drive, unscrew the two screws (2); adjust the drive with the adjusting screw (3)
11.2b. Check the condition of the hoses and wiring that are connected to the idle speed increase actuator (1) - to disconnect the solenoid mounting bracket from the engine, unscrew the two bolts (2)
3. Disconnect the vacuum hose from the fitting on the actuator/damper.
4. Connect a vacuum pump to the vacuum fitting of the actuator/damper.
5. Connect the tachometer according to the manufacturer's instructions.
6. Start the engine and set it to idle mode.
7. Create a vacuum of 11.8 mm Hg using a vacuum pump. The idle speed should increase.
8. If the idle speed does not increase, replace the actuator/damper as described below. Turn off the engine and disconnect the vacuum pump.
Replacing and adjusting the idle speed increase actuator/damper
Replacement
9. Disconnect the throttle return spring from the lever.
10. Remove the two screws securing the idle speed increase drive/damper (see Illustration 11.2a).
11. Disconnect the idle speed increase drive rod from the free lever and remove the drive.
11.11 To disconnect the idle speed increase drive rod from the free lever, pull the rod in the direction shown by the arrow
12. Install the new actuator/damper and connect the vacuum hose.
13. Adjust the idle speed increase actuator/damper as described below.
Adjustment
Note: The following procedure is for adjusting the idle speed increase actuator when the electric components or power steering are engaged.
14. Check that the rotation speed corresponds to the specification in Chapter 1. Adjust the rotation speed if necessary.
15. Unscrew the solenoid valve mounting bracket (see Illustration 11.2b). Disconnect the electrical connector from the bottom of the solenoid valve. Using an auxiliary wire, connect one of the solenoid valve terminals to the positive battery terminal and the other to the negative battery terminal. This will force vacuum from the intake manifold into the idle speed increase actuator and cause it to operate.
16. Open the throttle slightly - so that the idle speed increases to 2000 rpm - then slowly close it.
17. Check the engine speed. If necessary, adjust it with the throttle opening screw (see illustration 11.2a).
18. Repeat step 16 and check the idle speed.
19. Disconnect the auxiliary wire connected in step 15 and connect the electrical connector.
Adjusting the idle speed increase drive when the air conditioner is turned on
Note: The following procedure is for adjusting the idle speed increase actuator when the air conditioner is turned on.
20. Connect the tachometer according to the manufacturer's instructions.
21. Start the engine.
22. Turn on the air conditioner. This opens the solenoid valve, allowing vacuum from the intake manifold to enter the actuator, which moves to the fully open position. Check the engine speed and compare with specification.
23. If the engine speed is not within specification, adjust it with the throttle position adjustment screw (see illustration).
11.23. To adjust the idle speed increase drive to the desired speed with the air conditioner on, turn the throttle position adjustment screw (arrow) until the tachometer shows the required speed
Checking the idle speed control solenoid valve
24. Set the ignition switch to the "OFF" position.
25. Remove the solenoid valve (find it by the vacuum hose coming from the damper) and disconnect the electrical connector from it (see illustration 11.2b).
26. Check the solenoid valve winding with an ohmmeter. Compare the measured resistance with the specification. If the resistance does not match the specification, there is a break or short circuit in the coil turns. Replace the valve.
Checking the braking, enrichment, injection mixture and float chamber ventilation valves
27. Disconnect the solenoid valve electrical connector.
28. Check the solenoid valve coils with an ohmmeter by connecting it between the specified connector terminals. Measure the resistance of the float chamber ventilation valve between the connector terminal and the negative battery terminal (see illustration).
11.28. To check the windings of the electromagnetic valves, disconnect the connector and measure the resistance between the specified pairs of contacts using an ohmmeter (for the float chamber ventilation valve, measure between the specified contacts and the negative terminal of the battery), then compare the measured values with the nominal resistance of each coil: 1. Solenoid valve for adjusting the mixture composition, 2. Solenoid valve for enriching the fuel mixture, 3. Solenoid valve for braking, 4. Solenoid valve for ventilation of the float chamber
29. Compare the measured resistance with the specification.
30. If the resistance of any valve is not within specification, replace the valve (see illustration).
11.30a. Position of the electromagnetic brake valve
11.30b. Fuel mixture enrichment solenoid valve position
11.30 sec. Position of the electromagnetic valve for adjusting the mixture composition
11.30d. If replacing one of the carburetor electromagnetic valves, disconnect the terminal (1) from the valve connector by pressing the tab located next to the tab with a small screwdriver and pulling the terminal out of the connector - to remove the float chamber ventilation electromagnetic valve and valve assembly (2), unscrew the three mounting screws
Checking and adjusting the throttle position sensor
Examination
31. Disconnect the TPS connector.
32. Check the resistance between terminals 2 and 3 with an ohmmeter (see illustration).
11.32. To check the throttle position sensor (TPS), disconnect the connector and measure the resistance between terminals 2 and 3
33. Check that the resistance changes smoothly when the throttle valve moves from the fully closed position to the fully open position. If the resistance does not change smoothly or is not within specification, replace the sensor and adjust it.
Adjustment
34. Warm up the engine.
35. Loosen the throttle cable and check that the high idle speed cam is disengaged (see illustration).
11.35. Check that the high idle speed cam is disengaged (the lever should rest on the cam).
36. Turn off the engine.
37. While counting and recording the number of revolutions, unscrew (counterclockwise) the speed adjustment screws (SAS-1 and SAS-2) (see illustration) until the throttle valve is completely closed.
11.37. Unscrew the speed adjustment screws (SAS-1 and SAS-2) so that the throttle valve is completely closed - do not forget to count the number of revolutions (accurate to 1/4 turn), so that later you can return the screws to their previous position
38. Connect a digital voltmeter between terminals 2 and 3 of the TPS connector (see Illustration 11.32).
Note: Do not disconnect the TPS connector from the main wiring harness.
39. Turn on the ignition (do not start the engine), measure the TPS output voltage and compare with the voltage specified in the specification.
40. If the output voltage is not normal, adjust it. Depending on the type of TPS installed on the vehicle, turn the adjusting screw or loosen the TPS mounting screws and turn it (see illustration).
11.40a. If your carburetor has a TPS of this type (1) use the screw (2) to adjust it
11.40b. If your carburetor has this type of TPS, loosen the mounting screws and adjust it by turning the sensor itself.
41. Turn off the ignition.
42. Tighten (turn clockwise) screws SAS-1 and SAS-2 by the same number of turns that you unscrewed them in step 37.
43. Adjust the throttle cable free play (see section 16).
44. Start the engine and check the idle speed (see Chapter 1).
Checking and adjusting the damper
45. Before checking:
- a) Start the engine and warm it up (the coolant temperature should be between 80-95°C.
- b) Turn off all lights and electrical units. Check that the cooling fan is off
- c) Shift the gearbox to neutral (manual transmission) or Park (automatic transmission).
- d) If the vehicle is equipped with power steering, check that the wheels are in the straight ahead position.
46. With the engine idling, open the throttle valve fully until the free lever rests against the SAS-3 screw (see illustration).
11.46. With the engine idling, open the throttle valve so that the free lever touches the SAS-3 screw.
47. Close the throttle valve so that the SAS-2 screw rests against the free lever (see illustration) and record the engine speed at this moment.
11.47. Close the throttle valve so that the SAS-2 screw touches the free lever and measure the rotation speed in this position
48. If the measured rotation speed is not within the norm, adjust the damper by turning the SAS-3 screw.
49. Release the free lever and check that the engine slowly returns to idle speed.
Checking the air damper
Note: The choke control system is adjusted at the factory, so no further adjustment is necessary unless you have disassembled the carburetor or an exhaust test has shown that the choke components need adjustment.
50. Check the alignment of the marks on the electric air damper and the bimetallic block (see illustration).
11.50. Check the alignment of the marks on the air damper with electric drive and the bimetallic unit.
- a) If they are offset clockwise, the engine will start better, but the spark plugs will most likely be covered with carbon deposits
- b) If they are offset in a counter-clockwise direction, the engine will start poorly and stall.
51. When the engine coolant temperature is below 10°C, press the gas pedal. The air damper should be completely closed. If this is not the case, the bimetallic heater or lever mechanism is faulty
52. Start the engine, press the gas pedal and set the idle mode; the air damper should slowly and slightly open (immediately after starting) and form a gap of 1.5 mm.
53. If the choke does not open as the engine warms up, check the bimetallic heater, diaphragm(s) and vacuum passages of the choke actuator.
Checking and adjusting the high idle speed
54. Start the engine and warm it up to a coolant temperature of 80-95°C.
55. Check that all lights, cooling fan and all electrical units are switched off.
56. Set the gearbox to neutral (manual transmission) or Park (automatic transmission).
57. If the vehicle is equipped with power steering, check that the wheels are in the straight ahead position.
58. Remove the air filter (see section 8).
59. Connect the tachometer according to the manufacturer's instructions.
60. Disconnect the vacuum hose from the choke positioner (see illustration).
11.60. Disconnect the vacuum hose from the air damper positioner.
61. Set the lever to the second highest step of the high-speed cam (see illustration).
11.61. Set the lever (1) to the second highest step of the cam (2) for increased idle speed
62. Start the engine and check for high idle speed. Compare the measured value with the specification.
63. If the increased idle speed does not correspond specifications, adjust it with the high speed screw (see illustration).
11.63. If the increased idle speed does not correspond specifications, adjust it with the adjusting screw
- a) If you turn the high speed screw clockwise, the amount of throttle opening will be greater and the speed should increase.
- b) If you turn the high speed screw counterclockwise, the amount of throttle opening will be less and the speed should decrease.
Checking the bimetallic air damper heater
64. Disconnect the electric air damper heater connector and test the heater with an ohmmeter (see illustration). It should read approximately 6 ohms at room temperature.
11.64 To check the electric air damper heater, disconnect the connector and check the resistance with an ohmmeter.
65. If the resistance does not correspond to the specified value, replace the bimetallic unit (by drilling out the housing rivets). When installing a new unit, check that the marks on the unit match the marks on the housing. Install new rivets.