Idle Air Control System Check - Daewoo CIELO EURO III Manual

1F – 62 ENGINE CONTROLS
Circuit Description
The engine control
module (ECM) controls the engine idle speed with the
Idle Air Control (IAC) valve. To increase the idle speed,
the ECM pulls the IAC pintle away from its seat,
allowing more air to pass by the throttle body. To de-
crease the idle speed, it extends the IAC valve pintle to-
ward its seat, reducing bypass air flow. A scan tool will
read the ECM commands to the IAC valve in
counts. The higher counts indicate more air bypass
(higher idle). The lower counts indicate less air is al-
lowed to bypass (lower idle).
Diagnostic Aids
If the idle is too high, stop the engine. Fully extend the
IAC valve with a IAC tester. Start the engine. If the idle
speed is above 800 rpm, locate and repair the vacuum
leak. Also, check for a binding throttle plate or throttle
linkage or an incorrect base idle setting.
Test Description
The number(s) below refer to step(s) on the diagnostic
table.
2. The IAC valve is extended and retracted by the IAC
driver. IAC valve movement is verified by an engine
speed change. If no change in engine speed occurs,
the valve can be removed from the throttle body and
tested. Connect the IAC driver to the removed IAC
valve and turn the ignition ON. Do not start the en-
gine.

IDLE AIR CONTROL SYSTEM CHECK

5. This step checks the quality of the IAC valve move-
ment in step 2. Fully extending the IAC valve may
cause an engine stall. This may be normal.
6. Steps 2 and 5 verify proper IAC valve operation.
This step checks the IAC circuit for a wiring or
ECM fault.
Idle Air Control Valve Reset Procedure
Whenever the battery cable or the ECM connector
or the ECM fuse is disconnected or replaced, the
following idle learn procedure must be performed:
1. Turn the ignition ON for 5 seconds.
2. Turn the ignition OFF for 10 seconds.
3. Turn the ignition ON for 5 seconds.
4. Start the engine in park/neutral.
5. Allow the engine to run until the engine coolant is
above 85 C (185 F).
6. Turn the A/C ON for 10 seconds, if equipped.
7. Turn the A/C OFF for 10 seconds, if equipped.
8. If the vehicle is equipped with an automatic trans-
axle, apply the parking brake. While pressing the
brake pedal, place the transaxle in D (drive).
9. Turn the A/C ON for 10 seconds, if equipped.
10. Turn the A/C OFF for 10 seconds, if equipped.
11. Turn the ignition OFF. The idle learn procedure is
complete.
TAA1F360
DAEWOO T-154 BL2,3