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| May
be caused by a foreign object that has accidentally entered the
combustion chamber. When this condition is discovered, check the
other cylinders to prevent a recurrence, since it is possible for
a small object to "travel" from one cylinder to another
where a large degree of valve overlap exists. This condition may
also be due to improper reach spark plugs that permit the piston
to touch or collide with the firing end. |
|
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| Too
much oil is entering the combustion chamber. This is often caused
by piston rings or cylinder walls that are badly worn. Oil may
also be pulled into the chamber because of excessive clearance in
the valve stem guides. If the PCV valve is plugged or inoperative
it can cause a build-up of crankcase pressure which can force oil
and oil vapors past the rings and valve guides into the
combustion chamber. |
|
 |
| A
clean, white insulator firing tip and/or excessive electrode
erosion indicates this spark plug condition. k This is often
caused by over advanced ignition, timing, poor engine cooling
system efficiency (scale, stoppages, low level), a very lean
air/fuel mixture, or a leaking intake manifold. When these
conditions prevail, even a plug of the correct heat range will
overheat. |
|
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| Glazing
appears as a yellowish, varnish-like color. This condition
indicates that spark plug temperatures have risen suddenly during
a hard, fast acceleration period. As a result, normal combustion
deposits do not have an opportunity to "fluff-off" as
they normally do. Instead, they melt to form a conductive coating
and misfire will occur. |
|
 |
| Usually
one or a combination of several engine operating conditions are
the prime causes of pre-ignition. It may originate from glowing
combustion chamber deposits, hot spots in the combustion chamber
due to poor control of engine heat, cross-firing (electrical
induction between spark plug wires), or the plug heat range is too
high for the engine or its operating conditions. |
|
 |
| Combustion
deposits are slight and not heavy enough to cause any detrimental
effect on engine performance. Note the brown to greyish tan color,
and minimal amount of electrode erosion which clearly indicates
the plug is in the correct heat range and has been operating in a
"healthy" engine. |
|
 |
| Rarely
occurs in automotive engines, however, this condition is caused by
similar conditions that produce splash fouling. Combustion
deposits thrown loose may lodge between the electrodes, causing a
dead short and misfire. Fluffy materials that accumulate on the
side electrode may melt to bridge the gap when the engine is
suddenly put under a heavy load. |
|
 |
| Appears
as "spotted" deposits on the firing tip of the insulator
and often occurs after a long delayed tune-up. By-products of
combustion may loosen suddenly when normal combustion temperatures
are restored. During hard acceleration these materials shed from
the piston crown or valve heads, and are thrown against the hot
insulator surface. |
|
 |
| This
form of abnormal combustion has fractured the insulator core nose
of the plug. The explosion that occurs in this situation apples
extreme pressures on internal engine components. Prime causes
include ignition time advanced too far, lean air/fuel mixtures,
and insufficient octane rating of the gasoline. |
|
 |
| A
build-up of combustion deposits stemming primarily from the
burning of oil and/or fuel additives during normal combustion ...
normally non-conductive. When heavier deposits are allowed to
accumulate over a longer mileage period, they can "mask"
the spark, resulting in a plug misfire condition. |
|
 |
Soft,
black, sooty deposits easily identify this plug condition. This is
most often caused by an over-rich, air/fuel mixture.
Check for a sticking choke, clogged air cleaner, or a carburetor
problem - float level high, defective needle or seat,
etc.
This may also be attributed to weak ignition voltage, an
inoperative preheating system (carburetor intake air), or
extremely low cylinder compression.
|
|
 |
| This
plug has served its useful life and should be replaced. The
voltage required to fire the plug has approximately doubled and
will continue to increase with additional miles of travel. Even
higher voltage requirements, as much as 100% above normal, may
occur when the engine is quickly accelerated. Poor engine
performance and a loss in fuel economy are traits of a worn spark |
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