Contents: Throttle assembly ⇓ Checking the air valve ⇓
Remove the two screws and pull the rubber boot off the air flow meter connector.
Figure 15.24. Air flow meter connector pinout
Turn the key in the ignition switch to the "ON" position and measure the voltage between each connector pin and the "ground" position (figure 15.24). Compare the readings with those given in the table. 15.3.
Table 15.3. Voltage at the air flow meter connector contacts
If there is a deviation from the rated voltage, check the main fuse, main meter relay and wires.
Figure 15.25. Using a screwdriver to release the air flow meter connector retaining clip
To disconnect the connector from the air flow meter, release the spring clip by prying it with a small screwdriver (figure 15.25).
Measure the resistance between the connector contacts (see Figure 15.24). The resistance values are given in the table. 15.4.
Table 15.4. Resistance between the contacts of the air flow meter connector in the initial position of the meter plate
Open the measuring plate sharply (by pushing) and measure the resistance between the contacts in accordance with the table. 15.5.
Table 15.5. Resistance between the contacts of the air flow meter connector after deflection of the meter plate
If the resistance deviates from the nominal value, replace the air flow meter.
To replace the air flow meter, loosen the clamp and remove the hose from the upper air cleaner cover. Disconnect the connector and remove the vacuum hose from the air check valve.
Figure 15.26. Air flow meter mounting elements: 1 – rubber ring; 2 – cover assembly; 3 – air flow meter
Separate the top air cleaner cover from the base and remove the gauge from the top cover (figure 15.26).
Installation is carried out in the reverse order of removal. Be sure to install the rubber ring between the meter and the top cover.
Caution! The position of the throttle valve adjusting screw is set by the manufacturer; adjustment during vehicle operation is not permitted.
Throttle assembly
Check the smooth movement of the throttle rod. The sticking can be caused by resinous deposits on the back side of the valve, which enter from the crankcase ventilation system through the hose into the surge tank and intake manifold. To remove deposits, remove the throttle body pipe, open the throttle body and thoroughly clean it with fine sandpaper. Be careful not to damage the thin coating of the damper and the housing wall.
Figure 15.27. Location of throttle body fittings for a non-turbocharged engine
Figure 15.28. Location of throttle body fittings on a turbocharged engine
Warm up the engine to operating temperature, check the vacuum at each throttle valve connection (figure 15.27, 15.28) and compare the results with the data given in the table. 15.6, 15.7.
Table 15.6. Vacuum pressure at the throttle valve fittings of a non-turbocharged engine
Table 15.7. Vacuum pressure at the throttle valve fittings of a turbocharged engine
If the results are different from what is required, clean or blow out the channels with compressed air.
If you need to remove the throttle body, first disconnect the negative battery cable.
Remove the air duct installed between the throttle body and the air flow meter.
Disconnect the throttle return spring.
Disconnect the throttle control cable from the lever.
Figure 15.29. Typical throttle assembly fastening elements: 1 – vacuum hose; 2 – air bypass hose; 3 – coolant hose; 4 – throttle assembly; 5 – gasket; 6 – vacuum hose
Disconnect the vacuum hoses at the top of the throttle body (figure 15.29).
Disconnect the connector from the throttle position sensor.
Drain about 1.0 liters of coolant from the radiator. Disconnect the coolant hose and air bypass hose from the throttle body.
Unscrew the four nuts and remove the throttle assembly.
Use a razor blade to clean off any remaining gaskets from the expansion chamber and throttle body, otherwise air may leak in after the throttle body is installed.
Remove any remaining resinous deposits and dirt from the throttle body by washing it in clean solvent or carbon cleaner. Be especially careful to clean the areas near the throttle valve.
Caution! Do not immerse the throttle angle sensor in any solvent or cleaner. Otherwise, damage to the plastic walls and the electronic circuit located inside is possible.
If possible, blow out the vacuum channels with compressed air.
Installation is carried out in the reverse order of removal.
Checking the air valve
Figure 15.30. Using pliers to clamp the air bypass hose
Start the engine and let it idle. While the engine is warming up, use pliers to pinch the air bypass hose; the engine crankshaft speed should decrease slightly (figure 15.30). If this does not happen, check the air valve and vacuum hose for leaks.
Warm up the engine to operating temperature. Clamp the hose again; the engine speed should decrease by 100–200 rpm. If the speed decrease exceeds 200 rpm, check for voltage at the air valve connector contacts.
To check the voltage at the air valve connector contacts, disconnect the connector and check the voltage supplied from the battery. If voltage is low or absent, check the fuel pump wiring or relay.
Check the air valve resistance; it should be 30–45 ohms. If the resistance is not within the specified range, replace the air valve.
To check the functionality of the air valve, remove one of the hoses, attach a section of hose and blow out the valve, while the key in the ignition switch must be in the "ON" position.
When the valve temperature is no higher than 20°C, air should pass freely through the valve. At temperatures above 20°C the valve must be closed.
To replace the valve, loosen the clamps and remove the hoses. Disconnect the connector, unscrew the screws and remove the valve.
Installation is carried out in the reverse order of removal.