|AUDI A6 2.8 Engine|
This post discusses a failure caused by a marked lack of power, especially at high engine speeds or in the torque transmission phase, in 2.8 and 3.0 petrol engines of the Audi and Volkswagen brands.
The engines motors affected are the following:
AMX PASSAT 3.0 engine. (Petrol).
AUDI A6 ACK 2.8 engine. (Petrol).
AUDI A4 ABC 2.8 engine. (Petrol).
The vehicle does not deliver adequate power and on the other hand, the vehicle has poor torque delivery.
PROCEDURE AND SOLUTION
1- Full diagnosis without any results.
2- Some components of the injection system are replaced but without a positive result.
3- The diagnostic equipment does not recognize failures; even when parameters are read, all values are correct.
4- An activation of the components of the electronic management system is performed and it is observed that the long manifold-short manifold switching flap works properly, but despite the control valve of the flaps is working, the failure still persists.
5- The valve is replaced but the problem persists.
This engine is equipped with a system of flaps that, depending on the engine revs, switches from long manifold to short manifold in order to improve the response at all engine operating regimes.
|Engine intake air flow scheme|
These flaps are governed by a pneumatic valve that is, in turn, governed by an electric solenoid controlled by the engine control unit.
In this case the whole system worked properly but the vacuum required to operate the system did not reach the activation valve due to a leak in the tube responsible for providing aspiration for the activation valve.
Thus the diagnostic equipment never reported a failure, as from the electric viewpoint the system worked properly and the fuel injection ECU did not detect any change in the electrical operation of its components.
Replacing the damaged tube section the problem is completely solved..