On the 6-cylinder M54 engine installed in BMW E83 X3 vehicles, the molded plastic intake manifold is configured as two sets of three runners with variable lengths. Low end torque and high end power are improved by varying the intake runner length according to a map stored in the ECM. Engine vacuum, load and ambient temperature are used by the ECM to determine the rpm at which to switch intake manifold configuration. The actuator used by the ECM to switch manifold configuration is a vacuum solenoid called the dual resonance intake system or DISA (resonance valve) valve.
At low to mid-range engine speeds (up to about 3750 rpm), engine torque is increased as the DISA (resonance valve) valve closes a flap inside the manifold, effectively increasing the length of the intake runners.
From mid-range to high engine speeds (4100 rpm and higher), DISA (RESONANCE VALVE) is de-energized. This opens the resonance flap inside the intake manifold and allows air to be drawn into cylinders through additional intake runners. This provides extra air for the power needed at higher rpms.
Another function of the design is that resonance waves inside the manifold pulse back and forth between opening and closing intake valves and help in cylinder filling.
A faulty DISA (resonance valve) valve can cause a number of problems for your BMW X3 with a M54 6-cylinder engine; everything from a check engine light, rattling sounds from the engine, to a rough idle. When the valve fails, the flap can leak engine vacuum if the seal or diaphragm fail. If the flap fails mechanically, it can come apart and get lodged in the intake manifold, and worst case scenario end up in the engine. In this tech article I will describe how to remove, test and replace the DISA (resonance valve) valve.
Keep in mind that when your car was serviced before, parts may have been replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have, so be prepared with different size sockets and wrenches.
Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Do not work on your vehicle if you feel the task is beyond your ability.
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If you suspect your DISA (resonance valve) valve is faulty, remove it to inspect it. Do not take any chances. If you have a rattling at the intake manifold, I would start the diagnosis by checking the valve. Information on checking the valve is listed below, after removing.
The DISA (resonance valve) valve is located on the left side of the intake manifold, in the center (red arrow).
Start by removing the four T25 Torx fasteners (red arrows) for the fresh air intake duct. Next you will unclip the five air filter housing retaining clips. Lift them up and unhook from the lid of the intake air housing. Start with the two near the mass air flow sensor. Then release the front clips.
Loosen the air flow meter clamp (green arrow). Disconnect the air flow meter electrical connector (red arrow) by pulling it straight out. If it won't come out, lever the release tab open using a small flathead screwdriver.
While working at the intake resonance valve, disconnect the electrical connector (green arrow) by pressing the release tab (yellow arrow) and pulling it straight off. Then remove the two T40 Torx fasteners (red arrows).
Working at the left rear corner of the engine compartment, remove the weatherstrip by pulling it straight up (green arrow). Then rotate the two plastic fasteners 90 degrees and remove (yellow arrows). Pull the hoses up and out of the plastic cover (red arrow).
Testing: The DISA valve flap (green arrow) rotates 90 degrees to lengthen or shorten the intake manifold runner distance. Engine vacuum is applied through the intake manifold to a small port (purple arrow) on the flap side of the valve. Rotate the flap 90 degrees (blue arrow) to check for looseness or a faulty connection to the lever. Hold in the closed position (blue arrow). Then cover the port on the solenoid (yellow arrow). The valve should hold at about the same position (90 degrees) (red arrow). If it returns to the rest position (green arrow), the solenoid diaphragm is faulty.