Service Repair Manual

MPI SYSTEM
Sensor Check
Check points
Check conditions
Test
specification
Probable cause of malfunction
Self-diagnostic
output
o Engine: idling
(2 minutes or more after engine
start)
Normal
o Check in accordance with the
diagnostic code.
(Note that the diagnostic code will
be erased if there is disconnection
or damage of the engine control
unit back-up power-supply circuit.)
o If numerous diagnostic codes are
output, the most frequent cause is
damage or disconnection of the
power-supply or ground circuit.
Oxygen sensor
o Service data
o Item No.11
o Engine warm
(Make the
mixture lean by
engine speed
reduction, and
rich by racing.)
Engine
Voltage (mV)
o If the oxygen sensor output voltage
condition
is high during sudden deceleration
When sudden 200 or lower
1) Check for injector leakage.
deceleration
2) Check the oxygen sensor signal
from 4,000
circuit.
rpm
o If the oxygen sensor output voltage
is low during high engine speed
When engine 600-1,000
1) Check the oxygen sensor and
is suddenly
signal circuit.
rewed
o Engine warm
Engine speed Voltage (mV) o If the oxygen sensor signal is
(Using the oxygen (rpm)
normal, the electronic control unit
sensor signal,
check the air/fuel
700 (idle)
400 or lower
is regulating the air/fuel mixture
ratio normally.
mixture ratio, and 2,000
o If the oxygen sensor output voltage
also check the
is low at all times, check for intake
condition of the
(changes)
air restriction.
electronic control
o If the oxygen sensor output voltage
unit.)
is high at all times, check for
600-1,000
leakage of the injector.
Air-flow sensor
o Engine warm
Engine
Frequency (Hz) o If the air-flow sensor output sud-
o Service data
condition
denly changes greatly, improper
o Item No.1 2
700 rpm
30-50
contact of the air-flow sensor or
(Idle)
connector is probable.
o If the output frequency of the
2,000 rpm
63-83
air-flow sensor is unusually high or
Revving
Increases
low, check the air cleaner element.
caused by
o If the output frequency of the
racing
air-flow sensor is high, an increase
of engine resistance or leakage of
compression pressure is probable.
31-38