Expert: Stephen Sokol Date: 2/13/2007 Subject: Jetronic Aux Air Valve / Idle Performance
Question At what temp is the aux air valve supposed to close off completely? Wondering if it's supposed to be a factor when starting up in warm ambient temps (e.g. 75 degrees outside). Should I try messing with the adjustment screw?
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The text above is a follow-up to ...
-----Question-----
I'm shining a flashlight into my 1984 Alfa Spider's Auxiliary Air Valve. How wide should the opening be at 30 degrees-F? Mine opens like a peice of pie, and less than a quarter of the area of the circle opens at that freezing temp. When hot, it closes completely. Is this how they're supposed to operate?
Reason I'm looking at is, I've been having idle problems. If my Alfa sits out all day in the sun, it starts up instantly, then dies. Over and over. In that case, once I get it running by applying throttle while turning the key, it's totally fine the whole drive home. Starting in a COLD morning, it starts instantly, then ALMOST stalls, then is fine...
-----Answer-----
About half the area should be open around 30F. Any Bosch air valve will do so get the best price. You could also try advancing the timing 4 degrees, and make sure the warm idle is 1000rpm. Readjust the idle co screw on the air flow meter to slightly richer (turn in--clockwise).
Answer You have two problems which is why I gave you the tuning parameters. I have had hit and miss luck messing with the adj. screw especially on units more than 2 years old. The aux. air valve should not be open at 70F. Do the tuning stuff and then you might try loosening the spring tension on the air valve flap, but, only after trying the tuning stuff. Of course. concerning the hot start problem: it might be a fuel pump starting to fail. Bosch pumps seem to not start rather than quit while running.
