Confused about high idle

[ninelevenick]

I pulled the aluminum hose that connects to the AAV to get my mirror in there to see if the valve closed after a few minutes of my car idling. I was surprised when the idle rose about a thousand or a bit less rpm after disconnecting the hose. Why? Doesn't introducing a vacuum leak lean the mixture resulting in lower idle? What's happening here?

[gazzerr]

You've created a vacuum leak. That aluminum hose joins the rear of the air box where the cold start injector is. Extra air is entering the bottom of the airbox. It's the same as opening the throttle. The AAV normally stops that flow when it heats up.

If you put your hand over the open end of the pipe you should be able to feel the suction.

[javadog]

There's a difference between an intake leak that admits air that hasn't passed through the airflow meter (this causes a lean condition) and air that gets into the engine that goes through the airflow meter, which is just a way of bypassing the throttle plate and admitting more air to the engine, increasing the idle.

JR

[ninelevenick]

Ah, okay. Both those explanations make sense. Thank you for your help!