Mazda MX-5 1990 Workshop Manual page 199

TROUBLESHOOTING GUIDE
F
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STEP INSPECTION ACTION
6 Check for correct intake manifold vacuum Yes Go to next step
Vacuum: More than 450 mmHg (17.7 inHg)
No Check for air leakage of intake air sys-
tem components c::::r page F-93
7 Check if air cleaner element is clean
Yes Go to next step
c::J
page F-75
No Replace air cleaner element
c::J
page F-92
8 Check for correct ignition timing at idle Yes
Check if ignition timing advances when
L7
page F-75
accelerating
Ignition timing: 10 0
±
1 0 BTDC ¢ If advances, go to next step
c:::>
If no advance. replace ECU
L7
page F-127
GND
TEN
-
No Adjust
c::::r page F-75
9 Check for correct fuel line pressure at idle Yes Check if fuel line pressure decreases
c::J
page F-103
when accelerating quickly
Fuel line pressure:
¢ If decreases. check fuel line and fil-
265-314 kPa (2.7-3.2 kg/cm2, 38-46 psi) ter for clogging
(Vacuum hose to pressure regulator dis- ¢ If no decrease, go to next step
connected)
No Low pressure
Check for fuel line pressure while pinch-
ing fuel return hose
~ If fuel line pressure quickly in-
creases, check pressure regulator
c::J
page F-111
¢
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
L7
page F-108
10 Check if exhaust system is restricted Yes
Repair or replace
L7
page F-115
c:::r
page F-115
No Go to next step
11 Try known good ECU and check if condition im-
proves
L7
page F-127
05UOFX-040
F-55