audifirst

occasionally I am having issues with car choking at idle.. , the rpm drops down by approx ~100-200 rpm and does it couple times like that then it stabilizes, I couldn't get to through the check engine code, finally it did yesterday
and came up with
16795 - Secondary air Injection System: incorrect flow detected PO411 - 35 -00

I remember that code long time ago, and it end up to be lose connection at the air box, and it was ok for a while, but this time everything was ok, nothing was loose, I do hear presumably air pump engaging when engine chokes, and then it stabilizes, what is the purpose of the air pump it goes from air box through pump and back to engine block, and what sensor actives it ?

rs4tech

the secondary air system operates at cold startup to pump fresh air into the cats to help them warm up faster, there are only 2 sensors involved, the maf and the front o2 sensors. the main problem with the secondary air system is that the valves that open to let the air into the exhaust are controled by vacuum and so if there are any leaks in the system the valves fail to open. you will see to valves on each one of your cylinder heads, check the vacuum lines running to them, also check the vacuum line that goes to your vacuum resivoir. if all of them are ok you might have a bad combi valve or failed pump.

audifirst

hopefully I can find problem somewhere..