Mazda MX-5 1990 Workshop Manual page 197

TROUBLESHOOTING GUIDE
STEP INSPECTION
6 Check if air duct and air hoses are correctly
installed
c::::r page F-76
Yes Go to next step
No Repair
7 Check for correct intake manifold vacuum at idle Yes Go to next step
ACTION
Vacuum: More than 450 mmHg (17.7 inHg)
No Check for air leakage of intake air sys,-
F
L?
page
F-92
tem components c::::r page
F-93
8
Check if air cleaner element is clean
c::::r page
F-75
9 Check for correct ignition timing at idle
c::r page F-75
Ignition timing: 10
0 ±
1 0 BTDC
~
klJLfJ
CONNECT TERMINALS
Yes Go to next step
No Replace air cleaner element
Yes Check if ignition timing advances when
accelerating
c::!>
If advances, go to next step
¢
If no advance, replace ECU
No Adjust
c::::T
page
F-92
c::r
page
F-127
c::::r
page F-75
10
Check for correct fuel line pressure at idle Yes Check if fuel line pressure decreases
when accelerating quickly
L?
page F-l03
Fuel line pressure:
265-314 kPa (2.7-3.2 kg/cm\ 38-46 psi)
(Vacuum hose to pressure regulator dis-
connected)
No
¢
If decreases, check fuel line and fil-
ter for clogging
c::!>
If no decrease, go to next step
Low pressure
Check for fuel line pressure while pinch-
ing fuel return hose
¢
If fuel line pressure quickly in-
creases, check pressure regulator c::::r 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
c::::T
page F-108
11 Check if exhaust system is restricted Yes Repair or replace
c::J
page F-115
c::J
page F-115
No Go to next step
12 Try known good ECU and check if condition im-
proves
c::J
page
F-127
05UOFX,039
F-53