From: Wally Plumley [wplumley@bellsouth.net]
Sent: Thursday, October 17, 2002 9:46 AM
To: 928
Subject: [928] Re: more on last message

At 03:01 AM 10/17/02, Matt wrote:
>sorry.....should have mentioned it is a 1990 928GT.
>
>Just had in tank pump replaced / timing belt / water pump / disi caps /
>rotors.......
>
>felt like loss of fuel or ignition (maybe to one bank of
>cylinders?)....but don't understand how a stop / start could rectify it.


 From an earlier post on the subject:

******
Diagnosing Ignition Monitoring System

9228porsche01
July 7, 1992
Model
928 S4/GT/GTS
Group
2
Part Identifier
2880
Number
9203
Subject:
Diagnosing Ignition Monitoring System
ATTENTION:
Service Manager/Service Technician
Models Affected:
928 S4/GT/GTS
 >From 1989 Models ->


Concern:
Checking of components after activation of the ignition monitoring system
(injection circuit switched off fault codes 1131 of 1231).
Activation may be caused by the following:
- Damaged or defective exhaust gas temperature sensors.

- Possible damage to the ignition coil wire left side (in driving direction)
between the ignition coil and distributor cap.

- Poor grounding of the mounting plate for the ignition final stages.

- Poor physical connection of the electrical plugs on the ignition final
stages.


Parts Information:
New version temperature sensor Part Number 928 606 155 02 New coil wire with
hose covering Part Number 928 602 040 01 (for left side)


Repair Information: 
1. Check the left side ignition coil wire. Be certain
the coil wire is routed freely and not under tension. If damaged, replace
with new version (see parts information).

2. Check all ignition components and connectors for corrosion, tightness,
correct connection and damage. Repair or replace as necessary. If an
ignition circuit has malfunctioned, an LED indication will be given by the
ignition monitor relay located on the L-H control unit mounting plate.

Ignition circuit I (cyl. 1-7-6-4) Red diode
Ignition circuit II (cyl. 3-2-5-8) Green diode

3. Before replacing temperature sensors, check the voltage difference of
both temperature sensors as per step 4 of this bulletin. Sensors are located
in the exhaust ports:
Model '89-'90, cyl. 4 and 8
Model '91 cyl. 3 and 7

The function of the ignition circuits and light diodes located in the
ignition monitor relay remains unchanged. It is not possible to determine
from the LED display of the ignition monitor relay if one or both
temperature sensors are defective or which temperature sensor has failed.
When installing temperature sensors, coat the sensor adapter threads with
molykote paste HTP (white) and torque sensors to 10 N-m.

4. The voltage difference of the temperature sensors must be checked in
order to ensure proper operation of the ignition monitor system.

Checking sensor voltage difference:
- Start engine and bring to operating temperature.

- Loosen the mounting bolt for the ignition monitor relay and pivot the
relay up to gain access to the plug terminals Do not disconnect the relay
plug.

- Set volt meter to the millivolt range and connect leads between E1 and E2
of ignition monitor relay (Figure 3, white wires). A digital volt meter must
be used. Polarity is not important.

- Measure voltage with the engine idling and again at approximately 2000
RPM. A maximum difference of +2.5 mV or -2.5 mV (depending on polarity) is
permitted. If the voltage difference is above 2.5 mV, stop the engine,
loosen and rotate one temperature sensor. Retighten sensor and check voltage
difference. If the difference is above 2.5 mV, stop the engine and rotate
the other sensor. If after rotating the sensors to different positions, the
voltage difference is too high (above 2.5 mV) the temperature sensors are
defective and must be replaced.

*****
David Roberts
928 SPECIALISTS


Wally Plumley
928 Specialists
www.928gt.com