A defective secondary choke may cause the engine to stall or run rough during warm-up, and may have irregular idle speeds.
Attention: The engine must be cold.
To check, you must perform the following operations:
Disconnect the auxiliary air damper connector.
Connect a voltmeter or portable 12 V lamp to both pins of the connector.
Start the engine. The voltmeter should indicate battery voltage or the carrying lamp should be on. Otherwise, look for a broken wire.
Reconnect the connector. Start the engine and leave it to idle.
Pinch the hose of the additional air damper (see arrow), after which the engine idle speed should drop.
Warm up the engine and pinch the hose again. In this case, the engine speed should remain unchanged. Otherwise, replace the additional air damper.