Need Professional Help Diagnosing with Durametric Data

[Jamesp]

Well, my old friends the bank 1 and bank 2 SAI codes popped back up shortly after my last post on this string and I kept grinding away at it and found a second problem in the SAI, this one of my own making.



That little black and white cylinder in the middle of the picture is the SAI check valve. It provides vacuum to the changeover valve to open and close the shut off valve. Running the SAI pump and manually switching the changeover valve (the video I posted) to open and close the shut off valve taught me what the pump sounds like when the system cycles. On a cold start up I heard the pump running and it was clear the system was not cycling, the shut off valve was closed, period.

So either the changeover valve was not getting an electrical signal, but the wires buzzed out good, or it was not getting vacuum. The check valve is brand new and functions out of the car, but its vacuum source was blocked. Looking closely at the picture a clean area to the left of the rubber manifold tube the check valve fits into can be seen. This is where the rubber manifold coupling was and the hole inside the rubber boot for check valve vacuum was blocked by the plastic manifold tube. Moving the coupling to the right unblocked the vacuum hole.

I fixed that and drove 30 miles and no CEL. Its supposed to be cold tomorrow morning so the SAI will definitely run when I start it up.

On the upside I learned about O2 sensors and how they work as well as long and short term fuel trims (mine are spot on perfect!) as well as some additional information on the MAF sensor. It's been frustrating but I walk away with a much better understanding of the SAI system and the engine control system as a whole.

One other side note, Bosch is used as a subcontractor to design the engine control systems (including SAI) for many different badges. They use the same parts in many of their designs and they also subcontract for parts so you can find the exact same parts in different brands of cars which is good to know if you're not into paying extra for a "Porsche" parts box.