Air pressure tester for intake hoses & IC: 200q20v digest.

Phil Rose pjrose at
Wed May 21 13:02:50 EDT 2003

At 10:37 AM -0400 5/21/03, Djdawson2 at wrote:
>[ Picked text/plain from multipart/alternative ]
>The throttle body will not seal the air pressure.  How I know?  I was able to
>detect small leaks at the 3 vacuum hoses that connect on the firewall side of
>the intake manifold.

Also, the throttle plate's "normal leakiness" becomes evident (at
least by inference) when the TBV fails. In that event, "unbypassed"
boost pressure jams the throttle shut ( _excessively_ tight),
and...the engine stalls. So in its normally closed (i.e. relaxed)
position, the throttle body should not provide much of a pressure
seal--as long as your testing doesn't involve a sudden burst of high

BTW, speaking of the TBV, I recently replaced a 4 yr-old  valve. Its
failure mode caused no perceptible boost loss, but it failed to open
(could not hold vacuum). Now, the off-throttle stalling symptom is
gone and transition through the gears is noticably smoother.


Phil Rose
Rochester, NY
mailto:pjrose at

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