Mitsubishi 3000GT 1991, Service Manual

Page: 160 / 1146

FUEL SYSTEM
0
n-vehicle Inspection of MPI Components
AIR FLOW SENSOR
Air flow sensor
I I
Equipment side
connector
flow rate (liters/second)
Harness side
connector
Control relay
Air flow sensor
ECU
Engine control connector
OPERATION
l
The air flow sensor located in the air cleaner converts the engine intake air volume into a pulse signal of
frequency proportional to the air volume and inputs it to the engine control unit, which then computes the
fuel injection rate, etc. based on the input signal.
l
The air flow sensor power is supplied from the control relay to the air flow sensor and is grounded in the
engine control unit. The air flow sensor generates a pulse signal as it repeatedly opens and closes
between the 5 V voltage supplied from the engine control unit and ground.
TROUBLESHOOTING HINTS
Hint 1 If the engine stalls occasionally, crank the engine and shake the air flow sensor harness. If the engine
Hint 2:
stalls, poor contact of the air flow sensor connector is suspected.
If the air flow sensor output frequency is other than 0 when the ignition switch is turned on (but not
Hint 3:
starting the engine), faulty air flow sensor or engine control unit is suspected.
If the engine can be run idle even though the air flow sensor output frequency is out of specification,
troubles are often found in other than the air flow sensor itself.
[Examples]
(1) Disturbed air flow in the air flow sensor
(Disconnected air duct, clogged air cleaner element)
(2) Poor combustion in the cylinder
(Faulty ignition plug, ignition coil, injector, incorrect compression pressure, etc.)
(3) Air leaking into the intake manifold through gap of gasket, etc.
Loose EGR valve seat
Revision