Mazda MX-5 1990 Workshop Manual page 194

F
TROUBLESHOOTING GUIDE
20 ENGINE STALLS AT IDLE - WHEN AIC,
PIS,
OR ElL ON
- Engine unexpectedly stops running at idle when
AIC, PIS,
or ElL ON
TION • AIC, PIS, headlight, blower fan and electric cooling fan OK
[TROUBLESHOOTING HINTS]
CD
Idle speed control malfunction
• No input signal from switch
-Idle speed misadjustment
- ISC valve stuck
STEP INSPECTION
Check if "00" is displayed on Self-Diagnosis
Checker with ignition switch ON
c::::r page F-78
2 Check switches for correct operation with Self-
Diagnosis Checker Monitor Lamp and ignition
switch ON
3
4
5
MONITOR
LAMP
c::::r
page F-S9
SYSTEM SELECT
1
TEST SW
SELF TEST
~
Check if ECU terminal voltages are OK
(1 G, 1 P, 1 U, 20, 20 and 2W)
c::::r page F-128
Check for correct idle speed
c::::r
page F-76
Idle speed: 850 ± 50 rpm
GND TEN
-
b B'LD
CONNECT TERMINALS
Disconnect
ISC
valve connector at idle and
check if "clicking" is heard from ISC valve
6 Try known good ECU and check if condition im-
proves
c::::r
page F-127
F-50
ACTION
Yes Go to next step
No Malfunction Code No. displayed
Check for cause (Refer to specified
check sequence)
"88" flashes
Check ECU terminal 1 F voltage
Voltage: Approx. 12V
(Ignition switch ON)
c::::r
page
F-SO
c::::r
page
F-12S
¢
If OK, replace ECU
c::7
page F-127
c::::>
If not OK, check wiring between
ECU and Self-Diagnosis Checker
c::::r
page F-7
Yes Go to next step
No Lamp not ON/OFF with specified
switch
Check for cause (Refer to specified
check sequence)
L7'
page F-89
Lamp always ON
Check wiring between ECU terminal 1 D
and Self-Diagnosis Checker
c::::r
page F-7
Yes
Go to next step
No Check for cause (Refer to "Check Point
for Each Terminal") c::::r page F-131
Yes Go to next step
No
Adjust
L7'
page F-76
Yes Go to next step
No Replace ISC valve
c:r
page F-99
05UOFX-037