Whenever the engine is loaded more at idle and the speed drops, for example when shifting into gear or connecting the air conditioner, the vacuum regulator ensures that the idle speed is increased until the engine returns to its previously stable condition.
For checking the vacuum regulator, the same test instructions apply as for adjusting the idle speed.
Remove vacuum hose (69) and close with a suitable plug.
Loosen adjusting screw locknut (79), while holding the threaded rod with a 6 mm open end wrench.
Set the engine speed to 1250 rpm using the adjusting screw (79). Put on the vacuum hose.
Check with a feeler gauge whether there is a distance of 0.5 mm between the adjusting screw (79) and throttle lever (12). Otherwise, adjust the distance using the adjusting nut (78). On vehicles with automatic transmission, apply the handbrake and shift into gear. If equipped, fully connect the steering servo. At the same time, the engine must still run stably, otherwise adjust the speed using the adjusting nut (78).
If available, turn on the additional air conditioning system. The vacuum regulator should now lift all the way up and engage the throttle by opening it slightly. The engine must run steadily.
Connect the temperature switch plug.