Mazda MX-5 1990 Workshop Manual page 185

TROUBLESHOOTING GUIDE
F
STEP
INSPECTION
ACTION
4 Check for correct intake manifold vacuum at idle Yes Go to next step
Intake manifold vacuum:
More than 450 mmHg (17.7 inHg)
5 Check for injector operating sound at idle with
sound scope or screwdriver
No
Low vacuum
Check for air leakage of intake air
system
Yes Go to Step 7
No Go to Step 6
c::::r page F-93
6 Check if approx. 12V exists at injector connector Yes Check if injector resistance is OK
a
page
F-112
7
8
9
10
(W/R) wire
Disconnect each high·tension lead at idle and
check if engine speed decreases equally each
time
Check if spark plugs are OK
WEAR AND CARBON BUILDUP
PLUG GAP
1.0-1.1mm
,""""-=---
BURNS
(0.039-0.043
in)~~_
DAMAGE AND
DETERIORATION
DAMAGE
Check if ECU terminal voltages are OK
(20, 2Q and 2X) c::r page F-128
11 Try known good ECU and check if condition im·
proves c:::r page F-127
Resistance: Approx. 140
c::;>
If OK, check wiring between ECU
and injector
L7'
page F-7
c:::!>
If
not OK, replace injector c::::r page F-112
No Check wiring between ECU and injector
L7'
page F-7
Yes Disconnect each injector connector at
idle and check if engine speed
decreases equally each time
¢
If OK, go to Step 9
c:::!>
If not OK, check injector for fuel
leakage
c::r page F-113
No Go to Step 8
Yes Check for correct engine compression
L7'
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
No
Yes
Go to next step
Check for cause (Refer to "Check Point
for Each Terminal")
Check solenoid valve
No Go to next step
c::::r page F-112
a page 8-10
a
page G-20
c::::r page F-132
L7'
page F-11 9
05UOFX-031
F-41