-----Original Message-----
From: Wally Plumley [mailto:wplumley@avana.net]
Sent: Monday, July 03, 2000 2:54 PM
To: 928
Subject: [928] Re: Hard Shifting Automatic


At 02:05 PM 7/3/00 +0000, bennyrig@aol.com wrote:

>Tony - Marc - Wally - Kevin...Thanks for your insights.  I will ask the
>mechanic to check to make sure the darn hose is hooked up and check for
>other leaks.  Does this hose run from the "5 -plex, vacuum distributor"
>under the airbox?  If necessary, I can also have the shift adjusted at the
>transmition.  The hesitation off idle is gone, but the car still runs and
>idles a little rough.  I'll ask about disconnecting the battery and having
>the computer learn again.  I can't tell you guys how much I appreciate the
>help...(I am sure the mechanic will appreciate the advice too!)

There are two vacuum systems on the 928. One system comes off of the vacuum 
connector at the brake booster. This system feeds the HVAC system, the 
cruise control (on earlier cars), the vacuum reservoir, and the intake 
manifold tuning flap (on later cars). This system is supplied from a 
venturi booster, and goes thru a vacuum check valve, so that the vacuum 
supply stays constant regardless of actual manifold vacuum. The 
transmission line should NOT be hooked to this constant vacuum system.

The other vacuum system is true manifold vacuum, and fluctuates with 
throttle opening. This system drives the vacuum advance/retard system for 
the ignition, the glup valve for the air pump, the transmission vacuum 
modulator, etc. The transmission line should have fluctuating vacuum - more 
at steady speed and overrun, less on acceleration.

Wally Plumley
928 Specialists