"Dr. Gizmo"
By Phil Arendt
Fuel Injector Causes Trouble
Question 1I have a 2002 Toyota RAV4 with an engine that misfires. The first time this happened I was driving along on the highway when the check engine light turned on and the engine started to hiccup. Then the check engine light started flashing. When I released the gas pedal the light stopped flashing but remained on. As I accelerated the light was steady but if I accelerated hard the light flashed and the engine hiccupped.
The next day I went to a
repair shop but the engine was running fine and the check engine light was
off. A mechanic did some tests and found
code 301. He replaced the spark plugs
and a coil on one of the cylinders. The
engine seemed to run better but a week later the hiccup and light problem
returned.
I returned to the repair
shop. The mechanic retrieved the same
code. Now he wants to replace the
injectors, but he is not sure if the injectors are the cause of the
trouble. Does this sound right to
you? B.R., email
Answer 1
No. It’s not time to replace all of the
injectors. Only one cylinder is acting
up. If the trouble code indicated trouble
in all cylinders it might be caused by faulty injectors at all of the
cylinders.
Since the condition appears
intermittently, it might be time to do some experimentation. Perhaps your technician might consider
swapping the injectors in cylinders one and three. By doing this he will be able to determine if
the injector in cylinder one affects the performance of cylinder three. If so, the hiccup as you describe will
transfer from cylinder one to cylinder three and cylinder one will no longer
exhibit the symptoms.
If this turns out to be
true, only one injector will need replacement.
Minor Repair Could Save Transmission
Question 2The check engine light turns on in my 2007 Lexus ES350. When it turns on the transmission does not shift properly. Sometimes it takes forever for it to shift into the next gear even if I’m not accelerating hard.
I went to a repair shop
where tests found a code for a problem in a temperature sensor inside the
transmission. The mechanic said that it
would be wise to replace the transmission due to the fact that the car has
nearly 155,000 miles. I did not have him
do any work he suggested.
My car is in great
shape. I don’t have a problem fixing it
as long as the repair is needed. Is it
necessary to replace or overhaul the transmission at this mileage? R.P., email Answer 2
No. Actually the temperature sensor is a serviceable part that does not require major disassembly of the transmission. As long as nothing deep inside the unit has broken or is excessively worn there is no need to overhaul or replace it.
Minor Repair Turns Ugly
Question 3I have a 2002 Dodge Durango that has no brake lights. I’m pretty handy when it comes to repairing our family cars, but this one has me stumped. The brake lights quit working. I determined that the brake light switch failed. I installed a new switch from my dealer and now the engine won’t crank to start, the brake lights still do not work and only the turn signal on the left side works. The lights on the right side don’t work at all and no indicators lights turn on in the instrument panel.
The brake light switch is easy
to replace. I’ve looked for loose plugs,
blown fuses, bad grounds, broken wires and I have tried another brake light
switch. Power goes in and out of the
switch but now I have multiple problems that were not there before. Can you help?
B.W., email
Answer 3
The fact that more trouble
developed after replacing the switch indicates that perhaps the battery was not
disconnect before the task of replacing the switch. It’s really an important step that helps
prevent trouble like this. It’s possible
there was a short circuit that damaged other circuits.Since the engine does not crank, it’s possible the range sensor in the transmission has failed. It’s also possible something failed in the instrument cluster. At this juncture it might be wise to have the vehicle towed to a well-equipped shop where an experienced technician can utilize test equipment to determine what has failed.
Moaning Over Groaning
Sound
Question 4When using the air conditioner in my 2005 Mini Cooper S I hear a groaning noise. I took the car to my repair shop. They could not find anything wrong with the air conditioning.
Other than the noise the air
conditioner works fine. I hear it mostly
when stopped at a light or in stop and go traffic. It’s annoying. Do you have any idea what might cause the
sound? G.M., email
Answer 4
Sometimes a noise such as
this is caused by failed motor mounts.
When the engine is not in proper alignment within the engine cradle
hoses, lines and other components also are not in proper position. This causes vibrations from accessories such
as the air conditioning compressor to transmit into the cabin.
Ask your favorite technician
to consider a check of the mounts It’s
possible an out of alignment mount needs adjustment. Also, replacement of a failed mount might be
the cure.
Body Work Blamed For Failed
Air Bag System
Question 5The airbag light in my 1997 Miata is on. Last summer the battery became weak and eventually failed. In its weakened state I delivered the car for body work to the passenger side fender. It was planned that the work would be done while I was on vacation, but it wasn’t started because the power antenna mast was broken and the motor had burned out. When I picked up the car the airbag light was on.
A shop representative said
the light was due to battery failure. He said they had tried
unsuccessfully to recharge it. He said I
should get a new battery and if the light didn’t go out after a month to bring
the car to their mechanical department. The mechanical department later
said that a simple re-set was not possible and that compensable work was
required. I stored the car over the winter and trickle-charged the new
battery before reinstalling it. The light reappeared and it needs fixing
because we need to know that the airbag is working in order to maintain the
car’s resale value. Otherwise the car is in A-1 condition.
What must be done to
extinguish the light and should the repair shop be responsible at its expense
to do the repair? A. R., West St. Paul, Minn.
Answer 5
The
fact the air bag light illuminated while the car was at the body repair shop
does not mean they did something wrong. However,
if they pinched a wire at the right fender it is their responsibility to cure
the trouble at no cost to you but the majority of components are located in the
cockpit of your MX-5.
Sensors,
switches and modules for the air bag system are in the interior and not on the
right fender. They did not do any
repairs to the interior. Also, replacing
the power antenna does not require any interior cabin disassembly as the power
antenna is situated in the trunk.
It
might be wise to check fuses in the fuse box under the hood. Also, it is time for a technician to perform diagnostic
tests on the air bag system. If the
fuses are okay more than likely a clock spring under the steering wheel is
broken or a module has failed.
It’s Impossible To Know
Everything About Every Vehicle
Question 6I’m an industrial engineer. How is it possible for an auto technician especially at an independent shop to know everything about every car they repair? M.C.P., email
Answer 6
They don’t, but they do know
a great deal. Obviously, computers
control numerous devices from infotainment systems to when the engine fuel
mixture needs a tweak or transmission needs to shift into the next gear or the
power door locks lock and unlock. The
information that rushes through computers is astounding with thousands of
changes per second. A technician uses a
computer to monitor systems, components, voltage and patterns on a scope to
determine if a device or system is operating as designed and within
specifications in his diagnostic tools and computer systems in a vehicle.
A big challenge is they
don’t have vehicle specific information.
When a vehicle comes to the end of a factory assembly line a heavy duty computer
loads vehicle specific software into the vehicle. It’s different for every vehicle. A minor cosmetic change to a vehicle results
in changes to vehicle software programs.
Minor changes for example in the style of a grille can change the
operation of the engine cooling system fan.
The factory installed software makes a change to accommodate the grille so
the engine cooling fan cools within certain criteria. This could mean a difference of five
revolutions of the fan per minute.
Technicians even at a
dealership have limited access to factory software data and information. Often, this results in questions. A vehicle may have a problem or maybe
not. Also, the lack of knowledge due to
differences in their tool software and vehicle factory installed software may find
a system is operating within their computer scan tool software specifications
but not within the factory installed vehicle specific software and the cause of
an issue may not be diagnosed.
Someday this might change
but for right now a technician is limited to the equipment and software that is
available to him or her. Changes are
constant and frequent, more often than Adobe and Microsoft change the software
in your home and work computers. It’s
important for a technician to keep all of his equipment up-to-date with
software updates or even new equipment.
Thank you for all the 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 mailto:drgizmo@hotmail.com. 08/19/2013 ® DR. GIZMO © 1989 - Present
