High Idle Speed - Mazda MX-5 1990 Workshop Manual

F
TROUBLESHOOTING GUIDE
11 HIGH IDLE SPEED - AFTER WARM-UP
[TROUBLESHOOTING HINTS]
Excessive intake air supplied to engine
CD
Throttle valve not fully closed
@
Idle speed control malfunction
• Air valve not closing
- ISC valve stuck
-Incorrect coolant temperature signal
STEP INSPECTION
Check if throttle valve is fully closed when ac-
celerator released
ACTION
Yes Go to Step 3
No Check if throttle linkage is correctly in-
stalled and operates freely
c:::r
page F-96
c:> If OK, go to Step 2
¢
If not OK, clean, adjust or replace
linkage
c:::r
page F-96
2 Check if dashpot is correctly adjusted Yes Check if throttle valve is contaminated
c:::r
page F-121
Dashpot set speed: 2,500 ± 150 rpm
3 Check if "00" is displayed on Self-Diagnosis
Checker with ignition switch ON
c::r
page F-78
SELECT SW A
4
Check switches for correct operation with Self-
Diagnosis Checker Monitor Lamp and ignition
switch ON
c::7
page F-89
SELECT SW A
F-36
=>
If contaminated, clean throttle body
c::r
page F-94
=>
If not contaminated, replace throttle
body
CT
page F-94
No Adjust
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)
CT
page F-121
c::r
page F-80
c:::r
page F-128
c:> If OK, replace ECU
CT
page F-127
¢
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)
Lamp always ON
Check wiring between ECU terminal 10
c::7
page F-90
and Self-Diagnosis Checker
c::7
page F-7