325Ci misses on cold start

[antonmnster]

It only hisses under two conditions: cold start, and blipping the throttle. It misses with either.

I'm wondering if the DISA isn't sealed. (The DISA is an electrically actuated flap valve that changes the length of the intake runners depending on conditions) I'd really hate to silicone any part of it since they don't last forever and I don't want to "glue" it in.

 

[FowVay]

There should be a auxilliary air pump that leans the exhaust when the engine is running rich such as during a cold start. It runs approximately 20 seconds or so. Have you checked all of the hoses and the control valve for this? It should be mounted on the passenger side of the engine behind the windshield washer reservoir.

You have a vacuum leak someplace. Check your fuel trim again when cold.

 

[antonmnster]

I can hear the aux pump run and shut off.

The problem is not just when it's cold, but also whenever I blip the throttle. There's the fairly loud hiss and miss, only under those two conditions. Normal running is just fine.