AIR ADMITTANCE VALVE LEAKING:

AIR ADMITTANCE VALVE PROBLEMS WITH THE PIPE IN MY KITCHEN, IT IS CLOGGED THERE IS LEAKING AND BAD ODOR IN THE PLUMBING.

Air admittance valve can leak, when a horizontal section of the venting system connecting to the air admittance valve is sloped too much the wrong way.  The air admittance valve itself becomes leaky and the issue.  It will need to be removed and replaced.  Not recomending cleaning an air admittance valve because you never know if you got it fully cleared out or not.