Runs Rough On Deceleration/Backfire - Mazda MX-5 1990 Workshop Manual

F
TROUBLESHOOTING GUIDE
RUNS ROUGH ON DECELERATION/BACKFIRE
• Engine runs rough while decelerating and abnormal combustion occurs in exhaust system
[TROUBLESHOOTING HINTS]
CD
Air/Fuel mixture too rich
• Air cleaner element clogged
• Fuel injection control malfunction
(Fuel cut control)
-Injector fuel leakage
-Ignition timing misadjustment
STEP INSPECTION
2
Check if "00" is displayed on Self-Diagnosis
Checker with ignition switch ON
L7'
page F-78
Check switches for correct operation with Self-
Diagnosis Checker Monitor Lamp with ignition
switch ON
c:::r page F-89
~=
___ --\
SYSTEM SELECT 1
TEST SW
SELF TEST
ACTION
Yes Go to next step
No Malfunction Code No. displayed
Check for cause (Refer to specified
check sequence)
Yes
No
"88" flashes
Check ECU terminal 1 F voltage
Voltage: Approx. 12V
(Ignition switch ON)
¢
If OK, replace ECU
¢
If not OK, check wiring between
ECU and Self-Diagnosis Checker
Go to next step
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
c::r page F-80
0=
page F-128
0=
page F-127
L7'
page F-7
c:::r
page F-90
and Self-Diagnosis Checker
0=
page F-7
3 Check for correct ignition timing at idle
F-64
c:::r
page F-75
Ignition timing: 10
0
±
1
0
BTDC
GND TEN
~
bBlOJ
CONNECT
TERMINALS
Yes Go to next step
No Adjust
0=
page F-75