Checking the engine idle speed (VW Passat B4)

The engine idle speed is checked on a warmed-up engine (oil temperature not less than 80°C), with a working exhaust gas oxygen concentration sensor, with correctly adjusted gaps between spark plug electrodes and ignition timing, with current consumers turned off, and with the air conditioner not working (if there is one).

Connect the control tachometer according to the operating instructions. Connect the gas analyzer to the engine exhaust system.

Start the engine at idle speed and check the idle speed of the crankshaft and the carbon monoxide (CO) content in the exhaust gases, which should be within 800-900 rpm and 0.3-1.2%, respectively.

Note: The idle speed and CO content are automatically maintained within the specified limits by the ECU using the idle speed controller and oxygen concentration sensor, respectively, and are not subject to adjustment during operation.

If the checked parameters do not correspond to the specified limits:

• check the vacuum system for leaks;
• check the idle speed control valve;
• perform a self-diagnosis of the system (see below).

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