Dear miatadriver-ga;
Thank you for allowing me an opportunity to answer your interesting
question.
I appreciate the fact that you had the foresight to ask. “What *COULD*
be causing this?” because obviously no one could possibly diagnose
your problem over the internet for certain without first physically
examining your car.
Because all of your plugs don’t seem to foul at the same time, or even
within a few hundred miles of each other, and your car has such high
mileage, I immediately suspected that your Miata probably has one or
more cracked or broken piston rings or possibly some damage to the
cylinder wall. This allows oil to enter the combustion chamber which
can result in a number of things (carbon buildup, scratched cylinders,
loss of compresion, frequently fouled plugs, noticeable missing, and
significant power loss or rough performance). I even found where
someone had asked an expert the same question you asked here, and
he/she seems to concur:
2CARPROS
http://www.2carpros.com/makes/mazda/miata.htm
“Question: 1992 Mazda Miata 1.6 mileage: 98000. My Miata started
running bad as if it was missing I tested all the fuel injectors and
fuel press and press regulator checked for spark on all 4 plugs looked
good so I replaced my plugs wow it ran great for a few miles then it
started to get worse again as it was before. When I replaced the
plugs, I noticed #1 and 3 were fouled. What could be doing this
should I replace the plug wires and what else might I need to look
at?”
“Answer: You may be fouling the spark plugs for number 1 and number
3 with oil due to possible broken rings or your engine may be just
tired and using oil. You might try a hotter heat range on the spark
plugs. We would suggest doing a compression check and find out what
is going on.”
When you take the pugs out to examine and clean them, they should
always be uniformly colored (this is called “reading” a plug). They
might even be a light brown, but this is usually ok as long as there
are no serious burns on the insulator (or anywhere else) and the color
distribution is uniform over the surface of the insulator.
Occasionally, you might see a phenomenon known as “tracking”, where a
string of carbon has collected on the electrode or the insulator. This
indicates that you may need a plug with a higher heat range (Mazda
recommends using #6 spark plugs), or, after installing a spark plug
replacement with the proper heat range, that perhaps you have an
underlying piston ring or cylinder problem. In older engines
especially, when there is a great deal of wear, carbon forms burrs on
the inside of the cylinder that can damage the otherwise smooth
surface of the cylinder wall and eventually lead to damaged pistons
and rings as well. These grooves caused by the scratchy carbon provide
a means for compression to escape in the form of extremely hot gasses
and often leads to fouled plugs, missing and loss of power. If the
heat range is wrong to begin with, the plug will try to compensate by
arcing a higher voltage beyond its intended capacity. The extra heat
generated by the over-firing plug and the longer arc is usually what
is responsible for this tracked appearance on the insulator.
See your mechanic and ask him to check your plugs’ heat ranges before
you ask him to do anything else. (This might keep a dishonest mechanic
from telling you that your car needs a “ring-job” when it might not).
If he says they are too low (or that you CAN go higher), ask him if he
can recommend some plugs with a higher heat range. If he does, buy
them (at a parts store where they are significantly cheaper – and not
from him). If he sees that you have plugs with the proper heat range,
you’ve most likely got a piston/ring problem, cylinger problem or, if
you are lucky, a simple worn seal problem. At this point I’d go ahead
an ask him to check for those by doing a compression check. My guess
is that this (or a combination fo these) is/are probably the source of
your problem anyway, but it wouldn’t hurt to try the heat range
solution first, just in case. A word of caution here – a second
opinion and shopping for estimates would be highly recommended as a
ring job on an older car can sometimes exceed the bluebook value of
the car itself. Frankly, it might not even be worth the investment
unless you just happen to have some special attachment to this
particular Miata.
Below you will find that I have carefully defined my search strategy
for you in the event that you need to search for more information. By
following the same type of searches that I did you may be able to
enhance the research I have provided even further. I hope you find
that that my research exceeds your expectations. If you have any
questions about my research please post a clarification request prior
to rating the answer. Otherwise, I welcome your rating and your final
comments and I look forward to working with you again in the near
future. Thank you for bringing your question to us.
Best regards;
Tutuzdad-ga
INFORMATION SOURCES
2CARPROS
http://www.2carpros.com/makes/mazda/miata.htm
SPARK PLUG ANALYSIS
http://www.gnttype.org/techarea/engine/plugs.html
MIATA IGNITION
http://www.miata.net/garage/ignition.html#plugs
SEARCH STRATEGY
SEARCH ENGINE USED:
Google ://www.google.com
SEARCH TERMS USED:
MIATA FOULED SPARK PLUGS
FREQUENTLY FOULED SPARK PLUGS
FOULED "SPARK PLUGS" RINGS
"SPARK PLUGS" "CARBON TRACKING "
"SPARK PLUGS" "HEAT RANGE " |
,
0 Comments
)