Mitsubishi ECLIPSE Technical Information Manual

I-48
ENGINE <NON-TURBO> - Control System
The threshold for determining what amount of rpm
change indicates misfire varies with engine speed
and load. This is required because as engine speed
increases or load decreases, the overall effect of
a single cylinder misfire diminishes due to the mo-
mentum of the crankshaft.
The misfire monitor contains an adaptive feature
that can take into account component wear, sensor
fatigue, and machining tolerances. The PCM notes
rpm variance between cylinders during normal ve-
hicle operation and then uses these figures as a
foundation for calculating the threshold at which
rpm variance is considered to indicate misfire.
NOTE
The PCM requires normal vehicle operation to up-
date its memory. Because the PCM has no reference
for “normal operation”, the PCM considers a misfire
condition to be normal if installed in a vehicle that
is misfiring. The same situation can occur anytime
battery power to a PCM is lost and a vehicle is
misfiring when the controller is reconnected,
The misfire monitor triggers operation of the MIL
in two different operating situations:
1,000 Rev Misfire
Misfire is continuously monitored (in 200 revolution
segments) once the enabling conditions have been
met. If the monitor detects misfire in more than
1.6% of the engine cycles in a 1,000 revolution
period, a temporary fault is set. Freeze frame data
of the operating conditions during the last 200 rpm
of that 1,000 revolution period are stored. As with
other monitors, failure of the misfire monitor on the
next trip matures the code, the MIL illuminates, and
a DTC is stored. It is important to note that two
trips are required for the code to mature. Continued
misfiring during the initial trip does not illuminate
the MIL.
200 Rev Misfire
If the monitor detects misfire in more than 15%
of cylinder firing opportunities during any 200 revolu-
tion monitored segment, the MIL immediately begins
flashing, a DTC is started, and the freeze frame
is stored with information regarding the conditions
at which the misfire occurred. This indicates that
engine misfire has reached the point where damage
to the catalytic converter is likely to occur. The ve-
hicle defaults to open loop operation to prevent the
adaptive fuel controls from dumping additional fuel
into the cylinders and accelerating damage to the
catalyst. Driving the vehicle with the MIL flashing
is not recommended.
Once out of the operating condition where the 15%
misfire is occurring, the MIL will stop flashing but
remain illuminated. The vehicle may be driven, but
should be serviced immediately.
Because some misfire is a common occurrence
in a number of driving conditions, MIL illumination
due to misfire may occur when no component has
failed. Try to identify conditions that could trigger
the misfire monitor that are not related to component
failure. Example of these are included below:
l Damp ignition system components
l Low fuel/running out of gas (monitor triggers
as engine sputters)
l “Lugging” the engine
l Pulling heavy loads
l Low quality gasoline
In addition, the following situations could mistakenly
trigger the MIL:
l Large potholes
l Extended rough road operation

Mitsubishi ECLIPSE Specifications

General

Brand	Mitsubishi
Model	ECLIPSE
Category	Automobile
Language	English