Surges While Cruising - Mazda MX-5 1990 Workshop Manual

F
TROUBLESHOOTING GUIDE
SURGES WHILE CRUISING
• Unexpected change in engine speed which is usually repetitive
[TROUBLESHOOTING HINTS]
CD
Air/Fuel mixture too lean or too rich
• Fuel injection control malfunction
• Air leakage of intake air system
STEP INSPECTION
Check if "00" is displayed on Self-Diagnosis
Checker with ignition switch ON
c:::7
page F-78
2
Check switches for correct operation with 5elf-
Diagnosis Checker Monitor Lamp and ignition
switch ON
3
Disconnect oxygen sensor connector and check
if condition improves
• Fuel line pressure low
• Evaporative emission control malfunction
• Spark advance control malfunction
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::>
If OK. replace ECU
c::::>
If not OK, check wiring between
ECU and Self-Diagnosis Checker
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 1 D
CT
page
F-80
cr
page F-128
c:::7'
page F-127
c:::T
page F-7
c:::::T'
page F-90
and Self-Diagnosis Checker
c:::7'
page F-7
Yes Check oxygen sensor
c:::7
page F-138
No Go to next step
4
Check if ECU terminal voltages are OK Yes Go to next step
cr
page F-128
5 Check if throttle linkage is correctly installed and
operates freely
F-54
No Check for cause (Refer to "Check Point
for Each Terminal") cr
page F-131
Yes Go to next step
No Correct, clean, or replace as required
any binding or damaged linkage, and
adjust cable deflection at throttle body
CT
page F-96
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