"Dr. Gizmo"
By Phil Arendt
Newly Purchased Used Vehicle Fails Emission
Test
Question 1
Recently, I purchased a 2003
Chrysler 300M with a 3.5-liter V-6 engine.
The car has 66,000 miles and looks new.
Also, it runs great. The trouble
is the check engine light does not work.
I did not know this until I took the car for an emissions test. It failed because the light did not work at
all. The man at the test station did not
know why it was not working.
I took the car to a repair
shop that has been servicing our family cars for many years. A mechanic did some tests and found one of
the oxygen sensors is not working but he was not sure why the check engine
light is not functioning. He’s pretty
sure the engine module is not sending a signal to turn on the light. He says the light should turn on for a moment
when I start the car but it is not. He
tested the light bulb. It works. He also checked the wiring and found nothing
broken. He also found the computer is
not sending voltage to the oxygen sensor.
My mechanic replaced the
computer. Now the check engine light
works as it should but the oxygen sensor is not. He says the sensor needs replacement. Before he told me the computer was not
sending voltage to the sensor. Now there
is voltage but the sensor still does not work.
Now he wants to replace the sensor.
I really like this car. Unfortunately I should have purchased a
warranty when I bought it. My budget is
really tight and thought I was buying a good car. Does what my mechanic says make sense to you?
N.B., email
Answer 1
With any car purchase
whether it is used or new there is risk of a fault. That’s why auto manufactures provide a
limited warranty and new and used car dealers sell aftermarket warranty
policies. The policies offer protection
against failures such as these.
In the future before
purchasing a used vehicle consider having it checked over by your repair shop. A technician should find problems such as an
inoperable check engine light. With that
information you might be able to negotiate a lower price or the seller would repair
the trouble as part of the deal.
It appears that your
technician is on the right track.
Installation of a new oxygen sensor should cure the trouble.
Squeaky Steering Hits A
Nerve
Question 2
When making turns the
steering in my 2006 Cadillac makes a moaning squeaking sound. My car has 60,000 miles and has never given
me a bit of trouble until now. I took
the vehicle to a trusted repair shop where a mechanic removed the steering
column. He lubricated every part he
could think of and reinstalled it.
Despite his work the noise is still there. Now he thinks the cause of the noise is in
the steering rack but replacing it is expensive.
The noise is
irritating. Is there anything else that
could cause this problem? F.T., email
Answer 2
Some vehicles develop a
squeaking or moaning sound at the rubber boot where the steering column passes
through the bulkhead from the passenger compartment to the engine
compartment. Lubricating the boot and
steering column with silicon grease usually cures the noise.
Also, some vehicles develop
a moaning squeaky sound at the serpentine belt.
A few years ago General Motors engineers developed an upgraded belt to
squelch the sound.
Ask your technician to consider
these suggestions the next time you visit his shop. Also, if these suggestions do not cure the
sound he needs to be absolutely sure the steering rack is the source of the
sound before he replaces it. Squeaky
moaning sounds from a steering rack is unusual.
Smoke Pinpoints Vaporous
Leaks
Question 3
The check engine light
turned on in my 2005 Buick LaCrosse. It
has a 3.8-liter engine and 58,000 miles.
I took the car to an auto supply store where an employee connected a
tester. He found a code that indicates a
small leak in the evaporative emissions system.
The man said that sometimes running the engine while filling the gas
tank causes the trouble. He also said
that sometimes a gas cap can leak. He
cleared the computer and I replaced the gas cap.
The next morning the check
engine light turned back on. I returned
to the auto supply store to have the car tested. The same code was in the computer for a small
leak in the evap system. What else
should I look for? R.P., email
Answer 3
The diagnostic trouble code
indicates a small leak in the evaporative emissions system. Typically a leaky gas cap creates a large
leak. The evaporative system prevents
fuel vapors from escaping into the atmosphere.
There are valves, lines, a canister and a sensor in the system that
could leak small amounts of vapor.
To determine the cause of a
leak a technician injects a specialized smoke into the system. Then he visually examines all the parts
including the gas tank for evidence of smoke leaking from a failed part. Small leaks are difficult to detect but
usually a patient technician finds the source.
Common leaks occur at the
purge valve solenoid in the engine compartment and often at the pressure sensor
and fuel level sensor at the fuel tank.
Repair all depends upon a technician’s findings.
Speedometer Quits At Will
Question 4
The speedometer in my 1998
Dodge Neon R/T quits whenever it wants.
Some days it works fine. On other
days it might stop working and then start working again as though there is
something loose inside the dash. I have
taken the car to two different garages to have it checked but it always works
fine while it is at the shop. Both
mechanics checked a speed sensor. It
tests fine. Both mechanics suggest that
I bring the car in when the speedometer is not working but whenever I have the
time to go to a shop it is working fine.
Do you know what will fix
the problem? B.N., email
Answer 4
Whenever the speedo quits
just give the dash a good smack. That
should fix it.
All kidding aside you
probably have hit the nail on the head.
More than likely there is a part on the speedometer circuit board that
is loose or broken. Hitting a bump in
the road probably causes a circuit to open and close causing intermittent
operation.
To find out for sure if this
is indeed the trouble a technician might consider giving the dash a good whack
during a road test or consider driving on a bumpy road. He also might check the connections on the
speedometer head for loose terminals and ground connections in the dash for a
loose or corroded connection.
If the connections are in
good condition more than likely an internal fault within the speedometer head
is the trouble. If this is verified,
replacing the speedo is the cure.
Oil Leak Continues After
Repairs
Question 5
There is a leak that causes
a lot of frustration and a mess wherever I park. I have a 2004 Chevrolet Avalanche with a
5.3-liter engine, automatic transmission and four-wheel-drive. Recently, the transfer case on the
four-wheel-drive had a failure that chewed up all the gears. A dealership replaced the unit and everything
was working fine. After about 10,000
miles of use a seal on transfer case developed a leak. I took the truck to a repair shop where a
mechanic replaced the leaky seal but within 100 miles it was leaking. Now after the third seal replacement, it’s
leaking again. My mechanic says
everything seems fine in the transfer case so he does not know why the seal
keeps failing.
Gear oil is all over my
garage floor. If this keeps leaking
eventually the transfer case will run out of oil and it will need replacement
again. This is expensive. I love my truck. This has to be fixed. Can you help? G.W.B., email
Answer 5
I understand your
frustration. Gear lube is tough stuff
and a pain to remove from a garage floor.
This must be repaired before the transfer case runs out of lubricant and
fails due to a lack of lubrication.
There may be a simple solution.
The transfer case might be
covered by a 12,000 mile or 12 month parts replacement warranty. Usually, when a General Motors franchised
dealer replaces a part it is covered by this warranty. Consider calling the dealer that installed
the unit about the trouble. There likely
is a faulty part that is causing the seal to fail. If so, repairs could be free under the terms
of the warranty.
It’s also possible a vent on
the transfer case is clogged that causes excessive pressure that forces
lubricant around the seal. If so, this
type of problem is a minor repair. Call
your dealer right away before this leak causes a major failure.
More to Gas Cap Than Meets
The Eye
Question 6
The check engine light
turned on in my 2010 Jeep Wrangler with a 3.6-liter engine and 90,000
miles. I took the car to a shop where a
mechanic found a code that identified the gas cap as leaking. I paid the mechanic for his work and went
directly to an auto supply store. I
purchased a new cap, installed it and an employee was able to turn off the
check engine light. I drove home
satisfied everything was repaired.
The next day I was driving
on the highway when the check engine light turned back on. The engine ran fine. The next morning I took the car back to my
repair shop. A mechanic checked it over and
found the same code as before. He said
there is a problem with the gas cap. He
tested the cap and it passed. Now he
says that I should get a cap from a dealership.
He told me that he always buys original factory gas caps and has never
had a problem like this. Since I did not
buy the gas cap from his shop I returned to the auto supply store to return the
gas cap. The man at the store refunded
the cost and I installed my old cap.
Right now the check engine
light continues to shine. I’m driving
with my old gas cap. Soon I will need to
have the car tested for emissions. My
mechanic says the car will fail the test because the light is on and the gas
cap is leaking. Will the car fail the
emission test? Why did the cap from my
auto supply store test fine but cause the check engine light to turn back
on? Will a gas cap purchased from a
dealership fix the trouble? L.T., email
Answer 6
I don’t know where you
reside. Assuming that you live in
Illinois I can tell you with a reasonable degree of certainty that your Jeep
will fail the state emissions test for the reasons your technician
suggested. As for why the aftermarket gas cap caused the
light to turn on, sometimes aftermarket parts just do not meet all of the
original equipment manufacturer specifications.
As for whether a factory
original equipment gas cap will fix the trouble, it more than like will resolve
the issue. However, in your account of the
circumstances there was no mention of tests on the old gas cap. I can only assume your technician tested the
old cap and determined that it has a fault just as he determined the gas cap
purchased from an auto supply store was found okay.
Years ago a gas cap had a
simple design that allowed fuel vapors to escape into the air and prevented
liquid fuel spills. Today, it has
evolved into a sophisticated piece of equipment that is an integral part of the
evaporative emissions system that prevents fuel vapors from escaping into the
atmosphere. Believe it or not it houses
valves that regulate system pressure.
When pressure is not maintained within specifications, a sensor signals
a computer. The computer turns on the
dash light to alert you of trouble.
Additionally, the lowly gas
cap is a major safety device that prevents fuel spills in collisions and
roll-over accidents.
Thanks for all of your great
questions. Dr. Gizmo can’t wait to
answer more.
Phil Arendt is a columnist, consultant and
A.S.E.-Certified Master Technician.
Readers may send questions to Dr. Gizmo at P.O. Box 548, Cary, IL. 60013
or e-mail address drgizmo@drgizmo.ws. ® DR. GIZMO © 1989-2012
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