have an odd experience last week with my 1998 Infiniti I30. I took
it to my mechanic for routine maintenance, having noticed the engine
was working a tiny bit harder to start and to accelerate on highway
in the past two weeks. They discovered the air filter and housing
were completely burnt out.
scratching our heads. An Internet search and checking with other
mechanics have turned up no clues. Itís been a dream for years
with routine maintenance. It has only 125,000 miles and was last
serviced in May, since I drove it only 5,000 miles since then. Iím
the only driver and it sleeps in my garage, which is secure and has
no rodents. What the heck?
After viewing the photos you enclosed, I can say there was certainly
a brief fire in the air box, and it completely consumed the air
filter element. Please keep in mind any ideas I might present are
limited in scope, as there is far more to the puzzle than I can
observe from a distance. To prevent a possible recurrence, your
technician needs to explore many aspects to this that are only
elements are constructed of pleated paper and, while fire-resistant,
can hold fuel and oil vapors, somewhat like a sponge. Air filter
boxes can also hold a film of oil in the bottom, due to the
crankcase breather hose oozing some hefty vapors. If the Infinityís
positive crankcase ventilation valve were restricted with sludgy
deposits, itís possible more oil vapors and liquid than normal
could end up in the air box. Itís slightly possible also that an
EVAP system malfunction could cause a greater than normal quantity
of fuel vapors to be present in the air box.
The next set
of darts to throw is what may have ignited the vapors or liquid.
Your hotwire-type mass airflow, or MAF, sensor lives within the air
duct between the air box and engine throttle. Itís again slightly
possible the MAF sensor malfunctioned, causing excessive heat to be
generated. The intake air temperature sensor also resides within the
air box, but this is such a tiny current device, I canít imagine
it causing excessive heat.
backfire through the intake manifold or throttle could ignite filter
element vapors. This symptom is typically pretty noticeable, as the
engine would buck or pop in a strong, abrupt manner, just once or
perhaps several times. Possible causes for a backfire of this type
are a lean air-fuel mixture, an ignition or valve timing fault ó
not likely with your system ó or a restricted exhaust system. If
the engine has always run smoothly during acceleration, we can
probably rule this out.
Iím a little
puzzled by your statement regarding reduced power and hard starting,
as there wasnít much left within the air box to cause a
restriction. These symptoms could be indicating an exhaust
restriction, lean air-fuel condition, or a crispy MAF sensor. Did
the "check engine" light illuminate? Any diagnostic codes
stored would be helpful.
I think with
some careful testing and possible repair of the above mentioned
systems and components, and with fresh, clean parts within a new air
box, the odds of this recurring are very low. We may never know the
exact ingredients of this perfect-storm situation.