auxillary air valve, continued.
When e3s, e9s, and 530 were far more abundant, I recall seeing a coupe with a water faucet (similar to the type found on the outside of homes for garden hoses) installed as an on-off valve for the same auxillary air valve of which you speak. It was at a gas station that obviously did not cater to fer'in cars. I have also seen the tube blocked witha sparkplug.
These units may be simple but I have tested many (new and used) and found they all closed to varying degrees at the same temperature. (Used the same pot on the stove). SOme would never close even with a flame direcly applied to the expansion element.
Although a few folks contend all aavalves tend to leak, I have two examples out of probably ten, that do not leak. I mention this because I found it critical to the decent running of the D-Jet. Yes you can tune the D-Jet with the leaky valve, but you may not get consistent results if you have any changes in temperature as one might expect when you leave the driveway. By tuning, I refer to altering the pressure sending unit or by including a potentiometer/ resistance in between sensors (e.g., the sensor screwed into the manifold log. As an aside - pull it off with the engine running and it should default to a rich condition).
I once spoke with a purported Bosch technician about these valves. He acknowledged the problem and suggested the easy fix was to modify the system to accept the newer type auxillary air valve as found on the later 6 cyl models. He likewise suggested funning a hotter thermostat to ensure full colosing of an otherwise lazy valve and - - - even suggested adapting the same type valve as found on similar vintage fuel injected-aircooled Volkswagens (412?) and Porsche 914's. Unfortunately he negelected to fully explain the swap and I chose to find the original style valve that worked.
