Table of contents: Checking the air damper drive ↓ Checking the thermal vacuum valve ↓
The intake air heating is controlled by a vacuum device, an air damper in the intake air pipe, depending on the temperature. If the device is faulty, the following problems may occur:
Unstable idle speed when engine warms up.
Dips in gas supply
Power loss, top speed not reached.
Checking the air damper drive
Remove the air filter.
Remove the fresh air hose from the air filter housing.
Check the strength of the vacuum hoses from the vacuum diaphragm device to the thermal vacuum valve and from the valve to the carburetor.
Check the hoses for damage by bending them and replace if necessary.
Disconnect the hose with the brown fitting from the thermal vacuum valve at the bottom of the air filter housing and check the operation of the air damper by sucking air with your mouth. You should be able to hear the damper closing or opening.
If the valve remains closed, replace the membrane vacuum device.
Checking the thermal vacuum valve
Test conditions The suction pipe must be in order and the engine must be cold, no more than the temperature of the hand. The suction air is no more than 20°C.
Attach both vacuum hoses to the thermal vacuum valve. Vacuum hose connection from the vacuum device (brown connecting element) may be marked as follows: brown sticker next to the nipple, brass pipe on the valve, the pipe has a notch. Connect the black vacuum hose to the connection on the carburetor, if necessary, extend the hose with an intermediate link.
The air filter remains removed. Start the engine and let it idle. The control valve should open.
Remove the black vacuum hose on the valve. The regulating flap should return to its original position after 20 seconds.
Otherwise, clean the 2 holes of the thermal vacuum valve on the inside of the air filter housing or replace the valve.
Install the air filter.
[Text provided by the online resource Audimanual.ru]