ENGINE <NON-TURBO>
-
Control System
I-47
Misfire Monitor
WlAK44M
L
Background
Misfire is defined by the California Air Resources
Operation
Board as the lack of combustion in a cylinder due
The OBD II misfire monitor uses information
pro-
to absence of spark, poor fueling, compression,
vided by the crank position sensor to determine
or any other cause. As a result, the air/fuel mixture
engine rpm and detect slight variations due to engine
will not burn, and during the exhaust stroke, it enters
misfire. Crankshaft rpm is calculated between the
the exhaust system. The raw fuel and excess oxygen
69”
and
9”
falling edges of the crankshaft position
adversely affect the fuel system’s feedback
mecha-
sensor signal.
nism (the oxygen sensor) and can cause permanent
damage to the catalytic convertor.
2 revolutions
-
120”
--I
iz
60” reference notch
Crank signal
AFUOO95
i
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