trouble starting in '86 5kcstq (HELP! More problems!!!)

[Huw Powell]

>
> > You would only be rich under boost.  Metered air would blow out of the
>leak
> > source instead of burning in the combustion chambers.
>
>How do you reconcile metered air blowing out the leak with a lean condition?
>If the air has been metered, the ECU will add gas for that air.  If the air
>then leaks, there is still the gas in the system.  That makes rich in my
>book.


under boost, yes.  when not under boost that leak sucks extra air in that
is unmetered.  And if you have a leak doing that, you probably are gonna
have trouble getting into boost, right?


> > ~90 percent of the time the entire intake tract will be in vacuum, meaning
>a
> > lean condition, upstream or downstream from the compressor wheel.
>
>There is a vacuum only after the throttle body, in the intake manifold.  The
>rest of the system is always under pressure.  I believe you forgot to factor
>the throttle body into your hypothesis of how the system works.  That, or my
>hypothesis of how things work is wrong :-)


when you are not under boost, there is still a light vacuum in the intake
tract, unless the throttle is pretty much closed.

moving air has a lower pressure than still air, or something like that.

So the engine goes from nasty-lean at idle and light throttle, to
nasty-rich under boost, with a tiny "sweet spot" where the intake tract at
the leak is at exactly 1 bar, or 1 atm., in other words does not leak
either way.


Huw Powell

http://www.humanspeakers.com/audi

http://www.humanthoughts.org/