Adjusting the position of the air flow meter pressure disc (VW Passat B4)

Remove the air intake cap from the air flow meter. Make sure that with the engine not running, the pressure disc is level with or no more than 0.5 mm below the beginning of the expanding cone of the air flow meter diffuser (fig. 2-182). If necessary, adjust the position of the air flow meter pressure disk by bending the spring clip 2 (fig. 2-183), having first removed the lower housing of the mixture regulator.

Note: If the air flow meter pressure plate is positioned above the specified level, backfiring will occur during misfires. If the pressure plate is positioned too low, both cold and hot engine starting will be difficult.

Check the centering of the pressure disk by inserting a 0.10 mm thick feeler gauge sequentially into four points around the circumference. If the pressure disk is in the wrong position, loosen adjusting screw 3 and center the pressure disk, then tighten screw 3 to a torque of 0.5 kgf·m. Adjust the engine idle speed. When adjusting, do not bend the leaf spring of the disk stop. Attach the air supply cap to the air flow meter.

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