"Dr. Gizmo"
By Phil Arendt
Engine Surges At Highway RPMs
Question
1
My
2003 Honda runs fine until the engine speed reaches 3,000 rpm. Around 3,000 rpm it surges and bucks. The first time this happened the check engine
light came on. Since then the surging has
been a problem. To curtail the trouble I
accelerate slowly making sure the engine doesn’t hit 3,000 rpm. I can drive all day without the trouble as
long as I am careful.
If
I continue to drive with this problem, will I do harm to the engine? Should I have it repaired right away? L.N.R., e-mail
Answer
1
Since
the problem could be caused by a mechanical problem such as a weak or broken valve
spring or electrical problem such as a failing ignition coil certainly you
could do harm by driving the vehicle.
After all if the engine is misfiring and the catalytic converter could
be destroyed due to unburned fuel and if a valve spring is broken a valve could
break a piston. You definitely don’t
want to have to replace the engine due to neglect. You’ll kick yourself if something
catastrophic happens.
Since
the check engine light is on chances are good that a technician will find the
cause of the trouble in no time so take the time to have the condition
diagnosed and repaired.
Extended
Cranking Time Raises Anxiety
Question
2
When
the temperature is below 40 degrees my 2003 Pontiac Grand Am GT with a
3.4-liter engine cranks excessively before it starts. Once it starts it runs fine the rest of the
day.
I
took the car to a local mechanic who checked for computer codes. None were found. Even though my car only has 71,000 miles he
suggested that due to time I should replace the spark plugs. I authorized the work but this did not cure
the trouble.
My
mechanic showed me the old spark plugs compared to new spark plugs and I
definitely could see a lot of wear in my old spark plugs. The engine does run better with them. Now my mechanic says I should wait until the
trouble is worse before I bring it back.
I’m worried that one morning the car won’t start. Do you have any suggestions? T.C., e-mail
Answer
2
Your
car is telling you to move to a warmer region.
While this might not be possible, the trouble might be caused by a dirty
air flow sensor, failing engine coolant temperature sensor or even excessively
worn or dirty engine coolant.
Cleaning
the air flow sensor might do the trick.
Also, if tests of the engine coolant temperature sensor might find it
has a fault. If so, replacement is the
cure. If the sensors are fine, a test of
the antifreeze and visual examination might find it needs a flush. If so, a fresh supply of engine coolant might
cure the trouble.
Until
this condition is resolved keep crank times under 30 seconds. Excessive cranking can overheat and damage
the starter. Short crank times under 30
seconds should help prevent failure and an unnecessary starter replacement that
could dramatically drive up repair cost.
Code
Finds Fault In Heated Sensor
Question
3
The
check engine light is on in my 2003 Subaru Baja. The car is in great condition although it has
112,000 miles. It hasn’t given me any
trouble until now.
The
engine runs fine even though the light is on.
I took the car to a local auto parts store where an employee did a test
that found code 32 for a bad oxygen sensor.
I purchased a sensor and with the help of a neighbor I replaced it. After the work I returned to the parts store
to have the code erased from the computer, but after driving 10 miles the light
came back on. I returned to the store
and a test found the same 32 code. The partsman
gave me another sensor. I installed it
and the same thing happened.
Do
you have any suggestions? A.R., e-mail
Answer
3
The
code your parts store employee found indicates a problem in the upstream heater
circuit of the heated oxygen sensor. It
indicates the current is high. It is
possible that the aftermarket sensor is the cause of the trouble but more than
likely there is a problem in the circuit.
Before you replace the sensor again, check for poor ground connections
and loose, corroded or broken terminals in plugs. Also, check for broken wiring under
insulation and chafed wiring. It is
likely you will find the trouble in the circuit, but if the circuit is proper consider
installing an original equipment factory part.
Carbon
Impairs Valves
Question
4
My
2009 Toyota Corolla with a 1.8-liter engine developed a misfire. I took the car to my local dealership where a
mechanic did a test drive and performed tests on the engine computer. He also did a compression test which found
one cylinder has low compression. After
some more investigation he found a rocker inside the engine had come off. He reinstalled it and checked the valves with
a scope. He found carbon on the valves
and cleaned them with chemicals. After
the work the engine ran fine. He said
the trouble was caused by gasoline. He
told me to switch brands.
I
have owned several cars and never had a problem like this before. Is this caused by a design flaw in my
car? Should Toyota be responsible for
this problem? Have you ever heard of
this before? N.T., e-mail
Answer
4
Over
the decades indeed I have heard, seen and corrected problems such as you
describe in engines of just about every make and model vehicle so this is not a
problem that is isolated just to your car.
Since I am not an engineer I cannot comment on engine design.
I
can say that in just about every case I have encounter with carbon deposits
inhibiting engine operation and performance, there were conditions that created
carbon formation. Poor fuel quality or
unusual driving situations were to blame.
It
is possible that fuel burned in the engine and short trip drives are factors
that have created conditions for carbon deposits to form. Your technician’s recommendations make
sense. Try a different brand of
fuel. Additionally, I don’t know if your
drives are short, but if they are there is something you can do that will help
prevent deposits from forming. Once a
week give your Corolla some exercise at highway speed for at least ten miles
straight without any stops. This will
bring the engine up to full operating temperature which will help prevent the
formation of carbon deposits that can impair engine operation.
In
addition to carbon deposits, if trips are short there is a high probability
oily sludge deposits have formed in the engine.
Sludge deposits are harmful to the engine as well. You can prevent them from forming by changing
the engine oil and filter according to the severe driving maintenance schedule
in your owner’s guide and take your car for a long drive on a regular basis.
Stick
With Your Technician
Question
5
My
2009 Chevrolet Silverado 3500 HD has a 6.0-liter engine, four-wheel-drive and
automatic transmission. The last time
the speedometer worked the mileage was at 76,000 miles. Part of the problem is the speedometer quit
working about a month ago and so did the four-wheel-drive.
I
took the truck to a local independent shop where a mechanic has been working
hard to find the cause of the problems.
He has replaced the speedometer cluster, tested wiring circuits, sent the
truck to a dealership to have a module and cluster programmed and he has tested
sensors and actuators motors on the four-wheel-drive. Now he says that the only thing left to do is
replace a control module.
I
trust the mechanics at my repair shop.
They have serviced and repaired our family vehicles for years with great
success. I have always felt confident
they did their work at a fair price and never felt they were unable to fix a
problem until now. Do you think it is
time for me to go to another shop for a second opinion? L., e-mail
Answer
5
I
don’t think it is time to bail on your trusty shop. It appears they have a good relationship with
a dealership. They sent the vehicle to
them (another shop) for more than just programming modules. The work dealer personnel performed likely included
tests for troubles before they programmed modules. Apparently, they did not find any faults.
Additionally,
there are several modules in your vehicle and modules communicate with each
other and the engine control module. Often
when the brain in one module scrambles, it corrupts communications between
other modules which can cause performance problems in other systems. Also, sometimes a module that is faulty will
not accept programming just as your home computer may react to a fault.
Additionally,
a technician uses a computer to communicate and program modules. It is very possible a fault in a module will
not accept programming even though the technician’s tool sends programming
information to the module. This seems to
be the case here.
It
appears your shop technician is on the right track. Give him a thumbs-up on installing a new
module. It is the likely cure for all issues.
Glitch
In Auxiliary Heater
Question
6
The
rear heater in my 2007 Mazda CX-9 with a 3.5-liter engine does not work all the
time. What happens is air does not
always blow from the top vent. I can
hear the blower running but no air comes out.
When it does not work if I turn the knob right and left a few times air blows
out the vent.
Is
there a cable or flap that opens or closes that is sticking? Can I repair it or is this something my
dealer needs to fix? C.O., e-mail
Answer
6
There
are actuator motors that move doors that control the direction and temperature
of air blowing from the unit. More than
likely an actuator motor is not performing as designed. If you are a seasoned do-it-yourselfer, have
an above average complement of tools and a repair manual you should be able to
disassemble the dash and center console to expose the actuators. Once this is done with a reasonable degree of
electronic and mechanical prowess you should be able to identify the cause of
the trouble and replace the faulty part.
It’s not a stroll in the park so set aside a day to accomplish the
task.
Assuming
replacement parts likely need to be ordered be prepared to place the vehicle on
the sidelines for a day. Usually, if a
dealer parts department does not have a part in stock, and there is no unusual
parts supply issue, parts should arrive the next day.
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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