From: Mark Anderson [mark@928intl.com]
Sent: Tuesday, September 03, 2002 11:39 AM
To: 928
Subject: [928] Re: Fuel Pressure Gauge questions

1987-1995 cars have the option of not using an 0 2 sensor.  There is an
unused plug on the engine harness where you can plug in a variable resistor
to adjust idle mixture.  This was used for cars that did not have catalytic
converters. For those of you that have PET the part is in 9-01-02 #22.

Mark Anderson #92
928 International
www.928intl.com



From: Mark Anderson [mailto:mark@928intl.com]
Sent: Tuesday, September 03, 2002 2:20 PM
To: 928
Subject: [928] Re: Fuel Pressure Gauge questions


It should be part of the engine harness near the EZK and LH brain.  The
variable resistor device is attached to the sheet metal holder for the
brains.

Mark Anderson #92
928 International
www.928intl.com




-----Original Message-----
From: Wally Plumley [mailto:wplumley@bellsouth.net]
Sent: Tuesday, April 08, 2003 9:26 PM
To: 928
Subject: [928] Re: O2 Sensor ?

At 01:54 PM 4/8/03, Jim Doerr wrote:
>84 EuroS - LH-JETRONIC
>Is it required to have the O2 Sensor hooked-up?
>
>I thought it was imperative to be installed for the brain to map outside 
>of WOT or decelleration.

The system can run in either "open loop" or "closed loop" mode.

In open loop, the fuel/air ratio is set according to a pre-programmed map 
burned into the EPROMs, as modified by the air flow sensor, temp sensor, etc.

The system is in open loop when the oxygen sensor is not yet hot enough to 
give a reliable signal; when the full-throttle switch signals the ECU that 
the throttle is open; when the idle switch signals the ECU that the 
throttle is closed.

In closed loop, the ECU uses the map and the sensors as in open loop, but 
the mixture is further refined based upon input from the oxygen sensor.

If the oxygen sensor signal is not present, the system simply reverts to 
open loop mode.

Wally Plumley
928 Specialists