Mazda MX-5 1990 Workshop Manual page 175

TROUBLESHOOTING GUIDE
F
STEP
6
7
INSPECTION
Check for injector operating sound at idle with
sound scope or screwdriver
8
Disconnect each high-tension lead at idle and
check if engine speed decreases equally each
time
9 Check if spark plugs are OK
10
11
WEAR AND CARBON BUILDUP
PLUG GAP
1.0-1.1 mm
I~~
__
BURNS
(0.039-0.043
in)
I§§;~~DAMAGE AND
DETERIORATION
DAMAGE
Check for correct ignition timing at idle
CI
page F-75
Ignition timing: 10 0
±
1 0 BTDC
GND TEN
-
k D'lhl
CONNECT TERMINALS
Check for correct fuel line pressure at idle
c::::7'
page F-103
Fuel line pressure:
265-314 kPa (2.7-3.2 kg/cm
2
,
38-48 psi)
(Vacuum hose to pressure regulator dis-
connected) (
I
~~£
'-"\L
12 Try known good ECU and check if condition
improves
c::::7'
page F-127
ACTION
Yes Go to Step 8
No Go to Step 7
Yes Check if injector resistance is OK
Resistance: Approx. 14Q
c:;>
If OK, check wiring between ECU
and injector
¢
If not OK, replace injector
c::::7'
page F-112
c:::r page F-7
CI
page F-112
No Check wiring between ECU and injector
c:::r
page F-7
Yes Disconnect each injector connector at
idle and check if engine speed
decreases equally each time
¢
If OK, go to Step 10
¢
If not OK, check injector for fuel
leakage
No Go to step 9
c::::7'
page F-113
Yes Check for correct engine compression
c::::r page 8-10
c:;>
If OK, replace injector
c:;>
If not OK, check for cause
(Refer to Section B)
No Repair, clear, or replace
Yes Check for correct idle speed
Idle speed: 850
±
50 rpm
~
If OK, go to next step
9 If not OK, adjust idle speed
No Adjust
Yes Go to next step
No
Low pressure
Check fuel line pressure while pinching
fuel return hose
~ If fuel line pressure quickly in-
creases, check pressure regulator
~ If fuel line pressure gradually in-
creases, check for clogging be-
tween fuel pump and pressure
regulator
If not clogged, check fuel pump
maximum pressure
c::::7'
page F-112
c::::r page 8-10
CI
page G-20
c:::r page F-76
CI
page F-76
c::::7'
page F-75
CI
page F-111
c::::7'
page F-108
05UOFX-025
F-31
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