Don't forget to rear Dr. Gizmo in today's Northwest Herald Wheels Section.
05/25/2012
"Dr. Gizmo"
By Phil Arendt
Sensation Of Misfire Despite New Engine Block
Question 1
Recently, I installed a short block in my 2006 Mazda 6. It has a 2.3-liter turbo-charged engine and
six-speed manual transmission. Since the
repair the engine feels as though it is misfiring. I have had it tested at two different shops,
but there are no trouble codes. All the
sensors pass tests. Tests show the spark
plugs are not misfiring. It just feels
as though they are misfiring when accelerating.
A check for cylinder leakage found all cylinders are within
specifications.
The sensation I feel is more of a surging. The engine does not lose power. The misfire is not abrupt. Do you have any suggestions? L.V., email
Answer 1
You have done major work.
Don’t let this setback get you down.
It is possible the trouble is caused by a performance issue in the
turbo-charger. Tests may find a problem
in the wastegate or air bypass. If so,
repair as necessary.
It is also possible there is a fuel delivery problem such as low
pressure or volume. Testing the fuel
pump may find it needs replacement.
It is possible one of the ground connections on the engine or in
the engine compartment is corroded or not secure. Perhaps a wire is rubbing on the engine and
the insulation has worn away causing a circuit to open.
Maybe one of the oxygen sensors is not responding quickly. A lazy sensor often will not trigger a
trouble code but cause driveability issues such as this. Testing the sensors may find one or more
needs replacement.
Noise Might Indicate New Engine Has Defect Or Fault
Question 2
I have a 1987 Ford F-150 pickup with a 5.0-liter V-8 engine. Over the last two years I have been restoring
the truck to like new condition.
Eventually, I want to enter it in car shows but there is one
problem. Six months ago I installed a
remanufactured engine. Since then the
serpentine belt has been making a squealing sound. I have checked and rechecked the belt
alignment. I have replaced the pulleys
on accessories and the crankshaft. Everything
seems correct and the alignment is on the money. I even used a laser to make sure everything is
in alignment. The squealing occurs
mostly when I depress the clutch. When I
release the clutch the noise is nearly inaudible.
Due to the restoration I have not driven the vehicle in over six
years, but I’m getting close to completion.
I have checked and rechecked everything.
I’m at a loss. This is my
baby. I need to get her on the
road. Do you have any idea what would
cause this problem? D.G., email
Answer 2
I understand your frustration.
Auto repair is a challenging field.
You will cure the trouble. Your
truck will be roadworthy soon.
Make sure that the squealing is not caused by a failed throw-out
or pilot bearing at the transmission and clutch. Sometimes when these are excessively worn
they can make a lot of racket.
If indeed the belt is making noise, it is possible the recently
installed engine has too much play at the crankshaft. It’s possible when the clutch engages and
disengages the crankshaft moves fore and aft causing stress on the belt. Some play is normal and acceptable but
perhaps there is too much play. Unfortunately,
if this turns out to be the trouble the engine should be returned to the
remanufacturer under warranty coverage but it is better to find out there is a
defect now than in six months when the warranty expires.
Module Miscommunication Hinders Normal Operations
Question 3
The radio and power windows in my 2000 GMC Yukon Denali quit
working. I took the vehicle to my local
repair shop where a technician found that there was no power to a fuse
panel. He replaced a body module. This fixed the radio and windows. The problem now is the remote key fobs will
not unlock or lock the doors. They were
working fine when I brought the SUV to the repair shop. My mechanic says his Tech 2 scanner tool used
to test and program the key fobs does not communicate with the new module so he
cannot program the fobs.
What’s the problem? R.M., email
Answer 3
Your mechanic is using a factory tool to do the work and not an
aftermarket diagnostic tool so it should communicate with the newly installed
module without any problems. The usual
cause for such trouble is an open circuit or there is another module that is
not functioning as designed.
There are several modules in your vehicle that communicate with
each other to control various functions.
Sometimes when one module fails it causes communication problems in
other modules so it is feasible there is another module that is scrambled and
needs replacement. Of course it is
possible the newly installed module is not the correct one for the vehicle so
your technician might consider checking to make sure he has the correct part.
Also, your technician should consider checking ground and power
circuits to make sure the problem is not caused by an open circuit. He may find a loose connection is the cause
of all the trouble.
Key Fob At Root Of Trouble
Question 4
Last night my 2005 Subaru Outback with 127,000 miles would not
start. I placed the key in the ignition
and turned it as usual but the engine did not crank at all. All the lights on the dash illuminated
normally. The radio and headlights
worked. Even the turn signals and heater
fan worked. The engine was silent.
My neighbor attempted to jump the battery but nothing
happened. He cleaned the battery
terminals and still the engine did not crank.
Next, I called a tow truck to jump the battery. The driver attempted to start the engine but
nothing happened. He towed the car to
his shop. Now a mechanic thinks there is
a problem with the security system. He
said he checked for trouble codes but everything seems fine. He says I should have the car towed to a
dealer where factory equipment will find the trouble. He thinks the ignition key should be replaced
and programmed. I only have one
key. Does this make sense to you? F.L., email
Answer 4
Yes. It appears your key
fob is not communicating to the body control module that protects the car from
theft.
Your car is equipped with an Immobilizer antitheft system. It needs a security code from the key. If it does not receive it, the antitheft module
disables the ignition, starter and fuel pump so the engine does not start. Obviously the car could be towed away by a
thief, but it can’t be driven away.
To fix the trouble a new key and reprogramming should cure the
trouble. Also, consider obtaining an
additional key. If this ever happens
again you will have a back-up key available so your car will not be disabled.
Extrasensory Perception Will Not Fix Air Conditioner
Question 5
The air conditioner in my 2003 Toyota 4Runner quit working. The fan works on all speeds and air blows
from the vents but it is not cold air.
Also, the a/c light is blinking.
I called three repair shops about the trouble but none of them could
tell me what is causing the trouble. All
they could say is bring the car in so they could check it out.
My friend says that the trouble might be caused by low Freon. He says we can buy Freon at a store and pump
it into the air conditioner. Will this
fix it? H.L.M., email
Answer 5
Calling a mechanic is similar to calling a doctor. If you had severe pain in your chest a doctor
probably would suggest that you get to a hospital to be checked out or at the
very least visit his office so he could render an opinion. He would not suggest calling a friend to have
him check. A friend might smack you in
the head so you forget about the chest pain.
Seriously, the heating, ventilation, and air conditioning system
is complex. No technician can determine
with any accuracy what is wrong over the phone.
Certainly the system may be low on refrigerant and pumping some in might
return temporary function with cool air from the vents, but there is a reason
the refrigerant level dropped. In such a
case more than likely refrigerant leaked from a failed seal, line or hose. In this example adding refrigerant would not
repair the cause. The proper fix is to first
repair the leak and then evacuate and charge the system with refrigerant.
Additionally, there are many other parts in the system that could
cause the trouble. There may be a failed
relay, valve, pressure switch, failed compressor clutch or computer
module. Even a loose wire could cause
the trouble. The best course of action
is to choose a reputable repair shop and authorize diagnostic time to find the cause
of the trouble. Once the cause is
determined shop management will provide an estimate for the repair. Then you can decide to award the repair to
the shop or not.
Shocked Over Cost Of Key
Question 6
My 2001 BMW X5 with a 3.0-liter engine will not start. When I turn the key the engine does
absolutely nothing. Not even a
click. I had the car towed to a shop
where a mechanic tested the battery. It
is fine. He also checked for codes. A code popped up that determined a problem
with the ignition key. The mechanic says
to fix the trouble I need a new key and it needs programming. The new key is expensive. The entire operation is going to cost an arm
and leg.
My mechanic says that if I have another key I should use it until
I get another. I only have one key. He has it.
Is there any way to temporarily bypass the security system so I can
drive the car without spending big bucks?
B.D., email
Answer 6
I’m sorry but the system cannot be bypassed. To fix the trouble it is time to open your
wallet, dole out the dollars and surrender your first born child if you have
one to purchase a new key and programming.
Your key is a transmitter that sends signals to your car’s security
system. Actually, it is a little more
complex. The signals constantly change
so a thief cannot use equipment to decode them and nab your car.
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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