[bimmerule]

i'd start with the ICV. when the car is idling or coasting the throttles are closed, all the air entering the engine is coming in via the ICV. take it off and inspect, the butterfly inside should move freely when shaken.

Does anyone have the procedure for cleaning the ICV? I did not see it in the DIY guidepost thread.

 

[bimmerule]

Take off the manifold and check all your vacuum lines under there and the plastic L fitting (located between 2 vacuum lines). I would also get a new intake manifold gasket and replace it while you have everything apart. Take off the ICV and twist it side to side, the metal flap inside there should move freely, if it doesn't use some carb cleaner and spray it in there while moving the flap up and down.

Is the intake manifold gasket the rubber boots at the bottom of the throttle bodies? Speaking of which, how do you clean the throttle bodies since I plan to take off the plenum and do a full scale cleaning/vacuum leak check.