Air Induction System

1. Check the connections at the power brake unit, vacuum chamber, pressure switch, EGR thermostatic valve, EGR valve, and fuel pressure regulator. Make sure all connections are sound and that no unmetered air is allowed to enter at these points. Also check that the throttle plate closes and that the throttle housing mounting bolts are all tight.
2. Check the injection seals for damage, and check for an improperly seated injector.
3. Connect a compound pressure gauge to the intake manifold downstream of the throttle plate and hang the pressure gauge in a visible position inside of the vehicle.
4. Start the engine and allow to idle. Check the idle. The reading should be between -5.8 and -10.2 psi (-0.4 and -0.8 bar). If the vacuum reading is less than specified, recheck for vacuum leaks as outlined in steps 1 and 2.
5. Check for air leakage in the induction system using the pressure gauge to check downstream of the throttle plates and visually check the passage between the air mass meter and the throttle plate. The vacuum reading should be above -5.8 psi (-0.4 bar).
6. Visually check for air leaks between the throttle housing and pressure pipe, between the pressure pipe and the turbo, and between the turbo and intake manifold. Also check for air leaks at the PCV valve, the APC return hose, the rubber boot connections between the intake manifold and the air mass meter, and the connections between the air mass meter and the air cleaner, at the air cleaner cover and between the air intake and the air cleaner.