Checking for fuel cut-off during engine braking (VW Passat B4)

Make sure the vacuum hose to the idle speed control valve is in good condition. Warm up the engine to normal operating temperature. Then increase the crankshaft speed to 2500 rpm. When the throttle position sensor is triggered, make sure that the crankshaft speed increases or decreases depending on this. If there is no change in speed, disconnect the idle speed control valve connector and connect a voltmeter to the terminals of the sensor block (fig. 2-194).



Increase the speed of the crankshaft to 4000 rpm, then abruptly close the throttle. At the same time, the voltmeter should indicate the battery voltage when the crankshaft speed decreases to approximately 1400 rpm. If the voltmeter shows the battery voltage at a lower speed. replace the forced idle valve.

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