Saab 9000 - Page 230

Fault diagnosis 227
Dips in idling speed and engine rpm (contd.)
of '
--.....c
~1
Diagnostic procedure
1 Check for air leakage
- Start the engine, warm jt up and then run it at id-
ling speed.
- Constrict the flow of air through the idle air con-
trol valve by pinching
off
the air hose using a
pair of pliers. Do not restrict the flow of air so
much that the engine stalls.
Idling speed should drop drastically.
Has engine speed dropped?
I
YES
I
Continue with point 2.
I
NO
I
Continue fault diagnosis
by
checking:
• Incorrectly adjusted throttle
Air leakage (after throttle).
Rectify as necessary and continue with po-
int 6.
)
..
L / '.:
2~
I
·---,·
I_
• ,.,r---,..,,.-
900 RPM
900 RPM
~
l
..._
~~
~
.
'
I
/.
◊
10-15SEC
'
,~
'/
-
I
.
=---- ,·
I
7
2 Check idle speed control operation
- Remove the pliers constricting the flow of air.
Idling speed should increase sharply and then stabi-
lize in about 10-20 seconds at the nominal speed of
850 rpm (warmed-up engine).
Functionality OK?
I
YES
I
Continue with point 5.
I
NO
I
Continue with point 3.
Saab 9000
I