Toyota Supra 1990 Manual page 193

EFI SYSTEM - Troubleshooting FI-19
SYMPTOM - ENGINE BACKFIRES-Lean Fuel Mixture
CHECK DIAGNOSIS SYSTEM
Malfunction
Diagnostic code(s) (See page FI-26)
Check for output of diagnostic code.
code(s)
(See page F 1-23)
Normal code
CHECK FOR VACUUM LEAKS IN AIR
BAD
1. Oil filler cap
INTAKE LINE
2. Oil dipstick
3. Hose connections
4. PCV hoses
OK
CHECK IGNITION TIMING
NO
Adjust ignition timing (See page IG-20)
1. Connect term inals TE
1
and E
1
of the
check connector.
2. Check ignition timing.
STD: 10° BTDC
@
idle
[wi
connect terminals TE1 and E1]
OK
CHECK COLD START INJECTOR
BAD
1. Cold start injector
(See page FI-77)
2. Cold start injector time switch
(See page F 1-112)
OK
CHECK FUEL PRESSURE
BAD
1. Fuel pump (See page FI-70)
(See page FI-71)
2. Fuel filter
3. Fuel pressure regulator (See page FI-81)
OK
CHECK INJECTORS
BAD
II
njectors - Clogged
I
(See page FI-83)
OK
CHECK EFI ELECTRONIC CIRCUIT
BAD
1. Wiring connection
USING VOL TIOHMMETER
2. Power to ECU
(See pages FI-30, 49)
(1) Fusible links
(2) Fuses
(3) EF I main relay
3. Air flow meter
4. Water temp. sensor
5. Air temp. sensor
6. Throttle position sensor
7. Injection signal circuit
(1) Injection wiring
(2) Resistor (7M-GTE)
(3) ECU
(4) Fuel cut signal
8. Oxygen sensor(s)