I am hoping there is someone out there that can help me identify a
mystery valve on my car, I can seem to figure out what it is and why its
there, I only know the car is much happier without it.
I had a rather elusive High idle problem that I finally solved.
However , I has raised a very intriguing question as I can not figure out
what the purpose of the faulty part was... When the car was warm it
would idle at 1600-1700 rpms. It would slowly fall back to normal. Slow
enough that it would not reach normal levels while sitting at a stop
light, but fast enough that things would return to normal before I could
locate the problem. Well I finally found it! There is a valve back near
the frequency valve and auxilary air regulator that allows metered air to
bypass the throttle plate and subsequenlty raise the idle. the valve is
actuated by vacuum. Apparently opening when there is vacuum fed to it
. My valve was opening intermittently resulting in my high idle. I
eliminated the valve and the idle problem is fixed, the car seems to
start better and the part throttle response seems better (probably my
My question is, What is the purpose of this valve? What is its
intended function? Is this Audi's early attempt at bypass valve?
The valve is a cylinder about 2" long and 1" in diameter. there are
three inlets, one small for engine vacuum and two larger (3/8" or 1/2")
that are connected one to the bottom rear of the intake manifold and the
other to the same tee that feeds metered air to such things as the
auxilary air regulator and the air conditioning idle-increase-solenoid
(or whatever they call it).
I'm ashamed to not know what a part on my car is there for...
But if it doesn't make the car go faster, I guess don't need it anyway.
Thanks in advance,