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Re: Hangin Revs

In a message dated 97-03-07 17:26:17 EST, you write:

<< > Just noticed something unusual (87 5kcstq-stock). When I let off the gas
as I
 > shift, the revs hang for just a second, before dropping. This repeats if
 > neutral I hold the revs for a few seconds and then let off-revs stay up
for a
 > second before dropping down.
 The same thing is happening with a 1988 5kcstq (stock) that I know 
 of.  I thinnk this problem coused his premature clutch brakedown.
 He did not wait for the RPM's to drop.
 I would like to find out what couses it as well.
 TIA >>
This is normal for most Late 87, all 88> turbo cars....  If you look at the
throttle body, you will see a large cast cover on the side with the WOT
switch (if you don't have one, this is not normal, ck the idle switch),
inside that cast cover you will see a small (~2in tall) oblong sphere with a
1/4 in pin sticking out of it...  This is the "delayed shut valve"....  It's
purpose is to reduce the pressure spike in the IC due to slamming the
throttle shut.  I is a dumb diaphram device with a small hole in it, and what
it does is the pin holds the "slammed shut" throttle plate open for just a
second, then lets is drop....  IF you don't have this and are getting these
symptoms, I would ck the resistance at the idle switch, and the "deceleration
valve" that sits on the back (in the quarter panel) of the air boot.  It's
job is to release all vacuum from the intake boot to the turbo, bypassing
that air to the airbox until the rpm's get to about 1100-1200rpm then it
closes again and the idle stabilizer circuit takes over.  It's job is to
eliminate rich fuel spikes caused by high boost conditions and sudden close
throttle, it basically allows the air flap to settle in rest position while
you are off the gas.  I found that this additional switch was a running
production change in late 86-early 87 turbo cars....  Most 86's Don't have
them....  Both the above items are GOOD things to have in a stage xx computer