ignition OPEL ASTRA 1991 Electronic User Guide

Downloaded from www.Manualslib.com manuals search engine 7.9.5 Cold starting conditions.
Definition: Engine speed < 450 r.p.m.
During cold start conditions the low inlet manifold tempera-
tures cause considerable fuel condensation on the inner
walls of the manifold. This condition is known as wall
wetting. To ensure correct A/F ratios it is necessary to
increase the quantity of fuel injected during cold starting
conditions to counteract wall wetting. A correction factor
is applied to the base map for engine temperatures between
-40øC and 100øC.
To prevent the engine from flooding the enrichment factor is
not only engine temperature dependent, but also time depend-
ent. This is implemented by reducing the enrichment factor
over a number of crankshaft revolutions, regardless of
engine temperature. If the ignition is turned off and an
attempt is made to re-start the engine the process is re-
peated.
7.9.6 Post start and warm-up conditions.
Definition: Engine speed > 450 r.p.m.
Engine temperature < 80øC
During these conditions the engine temperature is monitored
and the A/F ratio is decreased by lengthening the base map
injection duration to ensure smooth running of the engine
and to compensate for inlet manifold wall-wetting.

Downloaded from www.Manualslib.com manuals search engine 8 IDLE SPEED CONTROL
Idle speed is controlled by means of the IACV (Idle Air
Control Valve) mounted on the throttle body assembly. The
IACV is driven by the IACSM (Idle Air Control Stepper Motor)
which is controlled by the ECU.
The IACV maintains constant idle speed (temperature depend-
ent) under all engine loads.
The ECU makes use of closed loop control algorithms to
ensure the best idle conditions for warm and cold engines.
Whenever the ignition is first switched the ECU selects a
pre-set idle position which is temperature dependent, there-
after it operates in the closed loop control mode.
Idle speed control is only possible with the throttle in the
closed position.
Timing advance support is utilised in the idle range to
enhance idle speed control. Spark timing is advanced by up
to 10ø if the idle speed drops below the set point, result-
ing in increased engine torque to offset the drop in speed.
If the idle speed rises above the set point the timing will
be retarded up to 10ø to reduce engine torque.
Correct idle speed control is not possible when the battery
voltage is below 9 volt.

Downloaded from www.Manualslib.com manuals search engine 9 IMMOBILISER OPERATION
The system contains an immobiliser function which prevents
hot-wiring. When the ignition is switched on the ECU will
wake up and prompt the ACU for its ID (Identification Code).
The ACU will respond by sending its ID to the ECU for com-
parison with an ID code stored in the ECU's ROM. Only if the
ACU's ID matches the ECU's ID normal engine
management
control will be allowed to take place.NO ENGINE CONTROL IS POSSIBLE IN THE ABSENCE OFTHE CORRECTACU ID.

Downloaded from www.Manualslib.com manuals search engine 11 DIAGNOSTICS
Various possible methods of fault finding are listed below
to reduce down-time of the vehicle.
11.1 Diagnostic codes
The CPU continuously monitors its own activities and sensor
inputs. If a fault is detected during operation the diagnos-
tic lamp is turned on and a default signal value is used to
allow the car to be driven with slightly reduced perform-
ance. The fault code is stored in RAM for later evaluation
by the Dealer. If the fault disappears the unit will immedi-
ately use the sensor data instead of the default data, thus
ensuring optimum performance. The fault will be erased from
RAM after 7 starts (ignition turned on 7 times) during which
no fault was detected.
The fault stored in RAM could be accessed by grounding the
diagnostic initialisation input terminal. The fault will
then be flashed out by the diagnostic lamp.

Downloaded from www.Manualslib.com manuals search engine 11.2 Volt- and ohmmeter
No repair work inside the ECU's is possible and
recommended.
A multimeter could however be used to ensure that the fol-
lowing inputs to the ECU are present:
11.2.1 Battery voltage:
11.2.2 The voltage measured between terminals
26B (pos) and 25B (neg) should be equal to the battery
voltage (6 and 16 VDC).
11.2.2 Ignition voltage: The voltage between terminal 22B
and
power ground should be equal to the battery voltage with
the ignition turned on.
11.2.3 TPS supply voltage: The voltage between terminal
09B
and signal ground should be between 4.6 and 5.2 volt.
11.2.4 TPS input signal voltage: The voltage between terminal
05B and signal ground should be:
Closed throttle 0.3 < VTPS < 1.0
Part load 1.0 < VTPS < 3.11
WOT 3.11 < VTPS < 5.2

Downloaded from www.Manualslib.com manuals search engine 11.2.5 CO potentiometer supply voltage: The voltage
between
terminal 23B and signal ground should be between 4.7 and
5.2 volt.
11.2.6 MAP sensor supply voltage: The voltage between
terminal
24B and signal ground should be between 4.7 and 5.2 volt.
11.2.7 MAP sensor signal voltage: The voltage between
terminal
15B and signal ground with ignition on should be:
MAP signal voltage Manifold absolute pressure
_____________________________________________________
___
1.00 20 kPa
2.00 40 kPa
3.00 60 kPa
4.00 80 kPa
4.50 90 kPa
5.00 100 kPa
A general tolerance of +/- 5% exists on the above voltages.