I1 Checking the Induction System

I1 Checking the induction system

Tools:
- Pressure gauge set 83 93 514

There must be no leakage of air between the mass air flow sensor and the engine.

1 Check the hose connections on:
- the auxiliary valve
- the brake servo unit
- the vacuum tank
- the pressure switch
- the EGR thermostatic valve
- the EGR valve
- the fuel pressure regulator
and also check that the butterfly closes and that the three throttle body retaining bolts are tight.

2 Check that the injectors are properly seated in the inlet manifold and that the 0-rings are undamaged.

If air leakage is still suspected after these checks have been carried out, carry out further checking as follows:




3 Connect pressure gauge 83 93 514 to the inlet manifold downstream of the throttle butterfly and hang the pressure gauge from the rear-view mirror inside the car.

4 Start the engine and let it run at idling speed (850 ± 50 rpm).

Check the vacuum which, if the system is operating correctly, should be between -0.4 and -0.8 bar (-5.8 to -10.2 psi).

If the vacuum is less than -0.4 bar (-5.8 psi), this indicates a leak in the induction system. Check the system again as described in point 1.

5 Use the pressure gauge to check the induction system for air leakage downstream of the throttle butterfly and check the system by eye between the mass air flow sensor and the throttle butterfly. The vacuum should be above -0.4 bar (-5.8 psi).

6 Check for leaks by eye between the throttle body and pressure pipe, between the pressure pipe and the turbo, between the turbo and the inlet manifold, or at the inlet manifold connections for crankcase ventilation and the BPC return hose. Also check that no leakage occurs between the inlet manifold connection to the rubber duct and the mass air flow sensor, between the mass air flow sensor and the air cleaner, and at the air cleaner cover.

Also check the connection of the air intake to the air cleaner and its position.