Ferrari Mailing List: K-Jetronic continuing story: AAV

[rolindsay (rolindsay]

Morning folks,

Continuing the K-Jetronic FI rebuild story; I have removed the auxiliary air 
valve (AAV) and have cleaned and completed some of the tests. Here is a 
mini-tutorial and the test results. 

The AAV does just what it's name implies. It provides additional air, 
downstream of the throttle butterfly, to increase cold idle speed. At the same 
time, the warm-up and control pressure regulator is adding fuel to enrich the 
idle charge. But that's an other story. 
The AAV is heated by three mechanisms; the engine, an electric heater and the 
ambient temperature. When the ambient temperature is warm, the AAV is closed. 
No fast idle is needed. Same is true when the engine is hot. The extra air is 
needed when its cold and the engine is cold. 
On the 3x8 cars, the AAV is mounted on the engine. On the Mondial, the AAV is 
bolted to the lower side of the coolant expansion tank. Either way, heat from 
the running engine causes the valve to close, cutting off the extra air. 
With the ignition on, voltage is applied to a heater coil in the AAV. This coil 
also causes the valve to heat up and close, even if the coolant temperature 
hasn't risen high enough yet. Again, fast idle duration is limited. 

Okay, it's 57 degrees F outside. The AAV is about 20% open with no current 
flowing. Removed from the car, I placed the AAV in the freezer for about 10 
minutes. No change. Perhaps that wasn't long enough to cause a change?  I 
completed the rest of the tests, described below, then put the unit back in the 
freezer. I'll check it in about an hour. 
Back on the bench, the heater resistance measures about 45 ohms so continuity 
is indicated. I applied 12v to the coil and it drew about 260mA of current. If 
I solve E=IR for E (voltage) I get 11.7 volts. That's close enough to 12 volts 
so the AAV did not break Ohm's Law!
Given about a minute, or perhaps a little less, and with voltage applied, the 
valve had completely closed.  That part is working correctly. 
The final test will be to examine the thoroughly cold unit to see if it is 
fully open. More on that (and pictures) later. 
If everything tests okay now, the question will remain "Why do I see no 
increase in warm up idle speed?". Remember, this FI was butchered when the car 
was 'federalized' so there may even be a plug inserted in the line!  Nothing is 
being assumed to be the way Bosch engineered it. 

More after the cold test. 

Regards,

Rick

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