Need Professional Help Diagnosing with Durametric Data

[Gelbster]

James,
With all the thrashing around you've done in the bowels of the engine - is it possible that some SAI component is reinstalled backwards by accident?
I ask because I mark all my components with Paint Pen Marker just to help my feeble memory.
These are the only ones that seem to work. I use them for plasma cutting and welding also.
https://www.amazon.com/Super-Met-Al-1296-1324-Squeeze-Action/dp/B000KL7OYO
The Sharpie version I found to be useless.

[Jamesp]

Originally Posted by Gelbster

James,
With all the thrashing around you've done in the bowels of the engine - is it possible that some SAI component is reinstalled backwards by accident?
I ask because I mark all my components with Paint Pen Marker just to help my feeble memory.
These are the only ones that seem to work. I use them for plasma cutting and welding also.
https://www.amazon.com/Super-Met-Al-1296-1324-Squeeze-Action/dp/B000KL7OYO
The Sharpie version I found to be useless.

This is a great question because the one item that can be easily installed backwards is the vacuum check valve. Every time I remove and install it I question it (the black side goes against the black of the intake manifold). Simply knowing black on black isn't good enough for me, I have to blow air through it and think about where the vacuum is coming from each time to be sure. The rest of the components won't fit in backwards and the system works when wired around the computer control so it appears the mechanical components are installed correctly.

[Gelbster]

Very gracious of you James not to take offense at suggesting you screwed up :-).
I meant it as a warning to others to mark the orientation but then realized that the reason others may have a fault is that some(which?) component was already backwards.

[Jamesp]

Buzzing out the harness using the correct wiring schematic for DME 7.8 showed that the harness to be in good shape. To buzz out the harness disconnect all connectors on the ECU.



Use an extension wire to the multimeter to check the resistance between the wire of interest in the harness and all of the pins going into the ECU and to the car body. This will find a broken wire, or a short between two wires or a short to ground. I use a sewing pin to reach into all of the connector pin holes to check for continuity.



Everything checked out, so other than the bad relay there was nothing wrong with the SAI found.

The car is back together, and I even painted the rear bumperettes during the down time. I used sandable primer, sanded to get rid of the texture on the bumperettes, 3 or 4 coats of duplicolor general purpose black, 2 or 3 coats of clear. let dry several days then sand to remove remaining imperfections with 2000 grit paper and finish with polishing compound.



With any luck , this is the end of this string.

[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.