Need advice on 87 5ktq cabin "bzzzzt"

["Doyt W. Echelberger" <Doyt@nwonline.net>]

Frequently, when my 87 5kcstq is just coming up to maximum vacuum in 4th
gear, a soft but audible 'bzzzzzt' will come from somewhere in the dash,
toward the driver side. When this happens, engine power sags during the
sound, but doesn't chop off totally like when the fuel cut-off activates.
This event is happening when I am holding the accelerator pedal constant
and the engine is just starting to level off and float at that setting,
when the vacuum is at it's maximum.

I don't think this is classical fuel pump cut off, because I have
experienced that at maximum boost with the wastegate lower hose clamped.
This power sag isn't even at a time when I am using boost. Fuel pump
cut-off is far more total and alarming.

This event happens about the same time (or after) the little yellow upshift
light would normally announce 'time to be in another gear.'   But the light
doesn't work on my car.

My strongest candidate to account for this "bzzzzt" is the solenoid group
for the vacuum servos, and the lines to those servos, and I have a Bentley,
but it doesn't show me how to get to the individual servos. I think I take
out the glove box and look behind it for the main module.  But the sound
seems to come from the driver side dash, so I would guess there is a vacuum
line to one or more of the individual servos under there somewhere.

So, anybody able to focus me a little tighter? Tearing into the dash is
something I've never done, and I'd appreciate any BTDT's.


Doyt Echelberger
86 4kq
87 5kcstq  153k