The intake valve allows the manifold to be more effectively filled with air at high engine loads and speeds.
The intake valve is located in the outside-air tray of the intake muffler. It is operated by means of a solenoid valve by the Digital Motor Electronics (DME) according to engine load and speed. The solenoid valve is connected via T-joint to the vacuum line between the secondary air pump and the pressure accumulator. The solenoid valve is situated underneath the engine cover of cylinder bank 1.
At idling speed and medium engine speeds, the intake valve is closed. During acceleration, the DME opens the solenoid valve according to a stored data map. The depression then created opens an extra intake channel in the lower part of the air filter housing upstream of the filter. This provides an improved supply of air to the engine at high revs and under high loads.
The following faults can occur:
Failure of the intake valve to open will reduce engine performance. The following causes are possible:
Cause |
Measures |
Solenoid valve not actuated by DME or Electrical fault on solenoid valve |
Fault recorded on DME: (236) EC activation of intake valve Check connecting leads and component activation |
Mechanical fault on solenoid valve |
Check connecting leads and component activation |
Lack of vacuum |
Check vacuum hoses |
Intake valve closed and mechanically jammed |
Visual inspection |
A permanently fully open intake valve has no negative effect on engine performance at high revs. Very high ambient temperatures combined with long periods of idling or standing can sometimes result in the intake air in the manifold becoming very hot. The consequence is then sluggish throttle response at lower revs.
If the intake valve is partially open, symptoms such as lack of power and sluggish throttle response at low revs may be experienced to varying degrees depending on how far open the valve is. In any event, a visual inspection of the intake valve must be carried out.