Removal and installation, testing of the throttle potentiometer (BMW 3 Series E30)

The throttle potentiometer is connected to its shaft and is a throttle position sensor for the carburetor control unit.

Removal

Remove the air filter (see section "Removal and installation the air filter").



Disconnect connector "2" of the throttle potentiometer, having first folded back the retaining bracket "3".

Unscrew screw "4" from the mounting bracket and remove potentiometer "1" of the throttle valve.

Examination

Remove and check coupling "4"; replace if necessary.

Check ease of movement and full angle of movement of about 90° of the leash "2". Check the force of the return spring.

Check the total resistance by connecting an ohmmeter to terminals 6 and 7.

Check the resistance of the potentiometer slider by connecting an ohmmeter to terminals 5 and 6.



If the resistance values deviate from the specified values, replace the throttle control potentiometer. For the specified values, see the table of the main technical data of the carburetor.

Installation

Insert the throttle valve potentiometer with the mounting bracket so that the throttle valve axis slider engages in the guide splines "3" of the coupling "4". At the same time, the projection "1" on the mounting bracket must enter the locking slot on the potentiometer and on the carburetor body.

Screw on the throttle potentiometer with the mounting bracket.

Install the air filter (see section "Removal and installation the air filter").

Checking the temperature valve

Start a cold engine and let it run at idle speed.





Disconnect the vacuum hose "1" from the straight fitting of the temperature valve and check for a vacuum at the end of the hose. To do this, close the end of the hose with your finger. If the finger is slightly "sucked in", there is a vacuum. Otherwise, check the tightness of the hose, as well as the patency of the hole in the carburetor.

Reconnect vacuum hose "1" and disconnect vacuum hose "2" from the angled fitting "2" of the temperature valve.

Check for vacuum at the angled fitting. As long as the coolant temperature is below approximately 45°C, the valve should be closed. That is, there should be no vacuum at the angled fitting.

Note: The orifice in the valve allows a small amount of air to pass through even when the valve is closed.

When the coolant temperature rises above 61°C, the temperature valve should open. There should be a vacuum on the oblique fitting.

Otherwise, the temperature valve must be replaced.

Note: The temperature valve can also be tested when removed. In this case, heat the valve in a water bath.