VW Scirocco - power loss caused by vacuum fault

Under certain operating conditions, the above-mentioned vehicle type may experience a significant loss of power. At the same time, the check engine warning lamp lights up and entries relating to boost pressure that is too low might well be stored in the error memory.

In these cases, the cause may be a constricted or blocked vacuum line of the boost pressure control valve. This impairs the control of the pressure box on the turbocharger, which leads to incorrect regulation of the boost pressure. As a result, the target boost pressure is not achieved, a situation which significantly reduces engine performance.

The following checks are necessary: the vacuum lines that supply the boost pressure control valve with vacuum and also the lines leading from the valve to the pressure box are to be carefully inspected for damage, kinks and internal constrictions. The leak tightness of the system can be tested with a vacuum pump and a pressure gauge by applying a vacuum and observing whether it is maintained over a certain period of time. Alternatively, a suitable smoke tester can be used. In this way, even the smallest leaks or blockages in the line run can be clearly localised.

If a defect is detected, for example a constricted or blocked vacuum line, the affected line must be replaced. Once the repair has been completed, the function of the boost pressure control valve should be checked by measuring the boost pressure values using a parameter query during a test drive.

For your own safety and the safety of other road users, test and trial drives must always be carried out with a second person present.

Reprinting, distribution, reproduction, exploitation in any form whatsoever or disclosure of the contents of this document, even in part, is prohibited unless our express permission has been obtained in writing beforehand and the source is stated. The schematic illustrations, pictures and descriptions are provided for explanatory purposes and are only intended as a visual supplement to the document text, so they cannot be used as the basis for installation or assembly work. All rights reserved.