How do I test the Auxiliary air valve?

I recently tested both Auxiliary air valves on my '91 TR type F133A engine with 48K miles. The results I got were the same. Open when cold (as they should be) and time delayed closing with tiny air leakage with 12V applied. It has a sliding shutter door that's controlled by a thermal time constant. I can't imagine this part could make an "air tight" seal due to the design. I have heard that these valves can degrade with age resulting in slow response times. Although I'm not sure if this has been confirmed. My air valves were surprizingly clean inside and they both measured equal, so I reinstalled them.

Hope this helps,

David

 

I am sure, you know how does the auxil.air valve work in the BOSCH KE-Jetronic system. Resetting that valve, however, is not an easy task... It can not be done by any "electronic" means, because of the way it is designed. The rotating shutter plate is pushed by a bi-metallic plate, that is curved at low temperature and pushes the shutter plate into the "open" position. This bi-metallic plate straightens at higher temperatures (it is heated by the current that goes through it) and no longer pushes the shutter plate, which is pulled by a small spring, which rotates it into the "closed" position. The problem is that this small spring weakens over time and, therefore, the shutter plate does not get pulled back enough to completely close the airflow.

So, as far as I know, one can adjust the valve only if you open it and replace the spring. Also, there is a small screw inside which regulates the initial position of that bi-metallic spring that pushes on the shutter plate. Of course, the valve can be opened using a thin rotary-type cutting instrument (i.e., Dremmel tool), but putting it back together will require drilling holes for small screws, tapping those, and using a high temperature silicone compound to form a gasket. Is it worth it? One can get these valves (BOSCH 0280140168) at a reasonable price.

I hope that this information will be helpful to you.

Juri.
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Good news, the correct '104 aux air valve was cheap for me, just $91.25 at Pelican parts (under pn. 13-63-1-362-597-BOE, inside was the 0280140104 part for 400i/Tr/Mondial/308). Yes, visually the valves should close, suggest you pinch off the intake and see if addresses your high idle--Lee

 

I got the 0280140168 from a BOSCH distributor for $45/each.

 

Great and very useful technical info guys, thanx !!