From time to time (on almost every car equipped with a turbocharger, particularly those with a variable geometry turbine, i.e. those with adjustable vanes which change the cross-sectional area of the turbine housing - mostly due to accumulation of dirt, soot on the inside and / or other simple causes) any or more of these symptoms can occur:

  • lack of engine power;
  • hesitation;
  • elevated consumption;
  • inability to reach certain speed (e.g. 120 km/h), due to limp / safe mode activation;
  • etc.;

accompanied by the car dashboard clearly indicating an error (and eventually pointing the owner to visit the nearest workshop).


In this particular case a quite generic Bluetooth (3.0) / OBD-II adapter supporting D-Can (2007+) protocol has been used in order to diagnose and fix the issue (as the car - depending on the equipment - has no more, no less than a few dozen ECUs, potentially giving a few hundred or even over a thousand DTCs - Diagnostic Trouble Codes).

The tool used (bimmer-tool 3.8.9), i.e. both the logs and the GUI quite clearly pointed out what was causing the issue - the actuator control mechanism (electronically) controlling the exhaust gasses flow, i.e. pressure via a few rods (the DTC is shown below in German, marked in yellow; along with a couple of other DTSs, all clearly pointing in the same direction):

 Fehler

Although the same type of error could (have) be(en) triggered by e.g. the electronic unit behind (i.e. driving the) mechanism being faulty also, the fix for this issue was as easy as spraying the mechanism, i.e. the joints (pictured below) with WD-40, Sonax MoS2OIL spray or similar, carefully warming the engine up (as usual) and driving it under varying conditions afterwards (to ensure that the mechanism has been freed up of any debris residing around it).

It may be a good idea to lubricate (protect from future seizing) the moving parts (joints) with some high-temperature-, corrosive-resistant (usually copper-based) lubricant, such as e.g. NIGRIN Kupferspray (apart from being resistant to high pressure; water, acids, alkali etc. - this one is said to be able to withstand over 1000 °C, which should be more than enough for the purpose).

 

Gestänge

 

Using high-quality fuels and / or specialized additives for this purpose may also help prevent the problem by keeping the turbo inside cleaner (as one part of this mechanism usually has a moving pin on the inside - inaccessible from the outside by usual means).