Weird Scary Boost SOLVED!!!

[Audial@aol.com]

First of all, thanks to Steve Eiche (EICHSTEV) for his incisive input on this
problem.

It turned out to be very simple.  On the back of the intake manifold to the
driver's side of the ICV is a little pipe that is connected to three vacuum
lines, two small, one large (one of these runs to the ECU).  Probing the
vacuum lines with my fingers and looking with flashlights revealed nothing
wrong.  However, then I decided to give the pipe a little tug.  It popped
right out of the manifold.  Evidently, under persistent boost it was being
blown out of the manifold.  This was causing the ECU not to read the correct
manifold pressure and let the turbo go wild. Then it would partially re-seat
itself after a varying amount of time, vibration and vacuum, resealing the
system temporarily and letting the ECU see the right manifold pressure again.

I got the idea to check this area first from the vacuum system diagram in the
Bentley, but I didn't realize that the pipe is just pressed into the manifold
- I thought it was molded in or something.  Steve suggested to me that I
might have an intermittent vacuum problem, probably in the line leading to
the ECU, and it turned out that he was right.

I removed the large hose from the pipe, cleaned off the end that inserts into
the manifold, flared it a tiny bit, and then tapped it back firmly into the
manifold with a rubber mallet.  It fits very snugly now.  Reconnected the
lines and started the car.  Not only is the mysterious overboost problem
gone, but the engine operation in general is smoother - I can put it within
10 rpm of where I want it to be on the tachometer.  Probably this thing had
been creeping out over a period of months.  I think I'll take a precautionary
step and seal it with some hi-temp silicone just to make sure.

BTW, the dipstick is now TIGHT while the engine is running.

As Scotty said:  "The more they overtake the plumbing, the easier it is to
stop up the drain."  

Thanks to everyone who gave input on this problem.  I'm glad it wasn't
something more.

Best Wishes,

Alex Kowalski
Exorcised '86 5KCSTQ