BMW E90 N52 DISA valve and loss of power
Can a DISA valve cause a loss of power in the N52 engine?
Yes. A faulty DISA can cause a loss of power in the 3000-4000 rpm range. When worn, the valve seals can stick to the flap, so the flap does not move properly. Besides loss of power, symptoms can include shaking when cold and an unsteady idle.
What is a DISA valve and where is it?
DISA valves change the length of the intake manifold in three positions: for low, medium and high revs. The N52 engine has two valves. The upper one is easy to remove, but the lower one is under the intake manifold and requires removing the manifold.
What should you note when replacing a DISA valve?
Buy the intake manifold gaskets at the same time, while the manifold is open. DISA valves are only available from BMW, so check their condition before buying parts. The intake manifold bolts are 11 mm, and 20 and 25 torx sockets are needed for the fuel line clip and the valve bolts. Old breather hose clips can break. Reserve several hours for the job.