stall??

[rob hod]

    This is how it works;

    The crankcase breather feeds via some bits of hose into a steel pipe
which goes into the big rubber inlet trunking
that runs from the air meter on the chassis to the throttle bodies. The
steel pipe is about half an inch bore and can pass an awful lot of air given
the chance. If you want to knock yourself out any time disconnect the pipe
and try sucking the end , and then take your oil filler cap off and see the
difference. Second thoughts don't.

    Anything that enters the inlet trunking without passing the air meter
contributes nothing to the process of keeping the air plate up, which means
a weaker mix. the amount that would pass when you take the filler cap off is
enough to let the air plate fall to rest, leaving a fuel free mix to enter
the engine and stall it.

    Although the (vacuum) pressures involved are low its worth remembering
the consequence that any major problems with the crankcase breathing will
have an effect on the running of these engines. Its also a reason why you
see a lot of 5 cyl engines with collapsed (but still working) breather
hoses - under certain conditions the vaccuum is quite high. Its also the
reason why oil seals can get quite bad without being a problem - plenty of
suction! (though they may leak at rest).

    Having said this, I can't vouch for what extra emission junk US spec
cars may have that may be different.

    Cheers

rob
----- Original Message ----- >
> Message: 7
> From: MEMAGIL at aol.com
> Date: Thu, 18 Jan 2001 10:29:32 EST
> To: <quattro at audifans.com>
> Subject:  stall??
>
> I have an 87 CGT, when i was checking out the car to buy, i opened the oil
fill cap while the car was idling and the car nearly stalled.  Is this
normal..?? I know the vacuum system is connected to the Evap and opening the
oil cap probably disturbs the whole balance of the vacuum pressure...but
should it stall out??  Other engines i have had you could open the oil cap
without worry of the motor immediatley stalling.
>
> --__--__--
>