Engine Problems; Preignition; Detonation; Electronic Fuel Injection - Arctic Cat Cougar Service Manual

TROUBLESHOOTING
If the engine is running rich, one or more of
the following conditions may be noticed:
a. The spark plug(s) foul often. Sometimes
this condition has been masked by install-
ing spark plugs of a hotter heat range.
b. The engine misses and runs rough when
operating under a load.
c. Exhaust smoke is excessive when the throt-
tle is depressed.
d. When the throttle is open, the exhaust will
sound choked or dull. Stopping the snow-
mobile and trying to clear the exhaust by
holding the throttle open does not change
the sound.
If the engine is running lean, one or more of
the following conditions may be noticed:
a. The firing end of the spark plugs become
very white or blistered in appearance.
Sometimes spark plugs of a colder heat
range have been installed which masks the
problem.
b. The engine overheats.
c. Acceleration is slower.
d. Performance flat spots are felt during op-
eration. These feel like the engine is trying
to run out of gas.
e. Engine power is reduced.
f. At full throttle, engine rpm will not hold
steady.
ELECTRONIC FUEL INJECTION
Refer to Chapter Seven for troubleshooting.
information on the fuel injection system.
ENGINE
Engine problems are generally symptoms of
something wrong in another system, such as
ignition, fuel or starting. If properly maintained
and serviced, the engine should experience no
problems other than those caused by age and
wear.
Overheating and Lack
of Lubrication
55
Overheating and lack of lubrication will cause
major engine mechanical damage. Make sure the
cooling system is not damaged and the oil injec-
tion tank is always filled. Make sure that the
cooling fluid has antifreeze that is properly
mixed and in the proper ratio to protect at the
temperatures encountered. Check to be sure that
the thermostat is opening correctly. Incorrect
ignition timing, a faulty cooling system or an
excessively lean fuel mixture can also cause the
engine to overheat. The wrong spark plug may
cause preignition and overheating.
Preignition
Preignition is the premature burning of fuel
and is caused by hot spots in the combustion
chamber (Figure 16). The fuel actually ignites
before it should. Glowing deposits in the com-
bustion chamber, inadequate cooling or over-
heated spark plugs can all cause preignition. This
is first noticed in the form of a power loss but
will eventually result in extended damage to the
internal parts of the engine because of higher
combustion chamber temperatures.
Detonation
Commonly called spark knock or fuel knock,
detonation is the violent explosion of fuel in the
combustion chamber instead of a controlled
burning and expansion (Figure 17). The exces-
sive combustion pressure can cause severe me-
chanical damage. Use of low octane gasoline is
a common cause of detonation, but detonation
can still occur when high octane gasoline is used.
Some causes of detonation are improper igni-
tion timing, lean fuel mixture, inadequate engine
cooling, cross-firing of spark plugs or the exces-
sive accumulation of deposits in the combustion