plug boot is changing color
This wire is from a Toyota Corolla
with a 16 valve DOHC engine. The spark plug wire shown above is
from an original equipment set, sent to us because a problem with
the wires was suspected.
Diagnosis by automotive technician:
Diagnosis by Magnecor:
It is obvious, by the discoloration of the bottom seal on the spark plug connector that water, and some oil, was collecting in the spark plug hole in which this connector was situated. The water level (which causes the spark plug base to rust) had reached the connector seal. Spark plug wire connectors are not designed to operate under water, and on this vehicle spark arcing into water no doubt occurred, causing the engine to misfire. Engines in cars suffering the problem of water filling spark plug holes will develop an engine miss at times whenever spark energy finds it easier to track down spark plug porcelain (inside the connector seal) and into the water. Also, arcing into water will occur after a pin hole is burnt through the connector's plastic extension tube, particularly if spark plugs gaps are too wide due to erosion or adjustment. Any trace of engine oil (leaking from valve cover) in spark plug holes will make matters worse! Not all spark plug holes will be affected.
Any spark plug wire connector, boot or seal which changes color indicates that water, engine oil, or a combination of both is present in the spark plug hole. If nothing is done to remove the water/oil from the spark plug hole/s, the engine will develop a misfire, and the wire connector/s will eventually be destroyed.
In cases like this, often all that has to be done is to clean out all the moisture and sometimes replace (if it appears contaminated with rust) the seal that fits over the spark plug (which are available from Magnecor as spare parts, even for many original equipment wires). Sometimes a thin smearing of silicone grease around the spark plug porcelain to help seal from moisture can help and replacing the spark plugs (particularly if they are old or the gaps are large) is also a good idea. Often replacing the wires is the simplest and the easiest fix, but you still have to make sure you deal with any moisture, oil or spark plug gap problem or the new wire, in time, will also fail for the same reason.
More information relating to this subject is available on our FAQ, specifically:
Why are sparks jumping from boots and cable jacket ? (question 14)
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