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<center><big><big><b><i><font color="#3333ff">Giammalvo Files</font></i></b></big></big></center>
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<img src="mark3.jpg" alt="Mark Giammalvo" height="180"
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<p><i><font color="#000000">Mark Giammalvo specializes in driveability
diagnostics </font><font color="#000000">at his family
business, Sam Giammalvo's Auto Sales & Service,
Inc. in New</font> <font color="#000000">Bedford,
MA. </font> </i> </p>
<p><i><font color="#000000">Mark, who has been with the business for
over 20 years, is an ASE
Master Technician and Parts Specialist. He also holds the ASE
L1 certification, and has an associates degree
in business</font> <font color="#000000">management.
<br>
Mark is also a writer for Motor Age Magazine
and is the past secretary of the Alliance of Automotive Service
Professionals, (AASP).<br>
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<big><big><b> How Many Diagnostic Tests Does It Take?</b></big></big>
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<p align="center"><small><i><font color="#000000">(Printed in the Journal
of The Alliance of Automotive Service Providers, AASP) <br>
<br>
</font></i></small></p>
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How many diagnostic tests does it take to find the solution to an automotive
problem? Sounds like the question of the decade given all the high-tech
vehicles we work on today. Truth is, some cars are resolved with one or
two tests while other cars will require much more. Sort of like the human
body when you think about it. <br>
<br>
A recent case at our shop began when a customer called in reporting their
1999 Lexus ES300 died on the highway. Little did we know what a diagnostic
dilemma this car would take us on.<br>
The Lexus would start, backfire and then immediately stall. The customer
reported that the check engine light had been on earlier in the week yet
the car had been running fine. <br>
<br>
The vehicle's fuel gauge seemed low so we added some fuel. The car would
still not run but carburetor cleaner sprayed into the engine seemed to make
a slight increase in running time before the car would stall again. At first,
the Lexus service manual led us on a wild goose chase regarding the fuel
pump's wiring diagram. To make a long story short, the factory wiring diagram
and supporting documentation were both wrong. The fuse pump relay was not
located in the slot in the underhood fuse panel as the manual had stated.
Next, we removed the rear seat so we could verify power and ground at the
fuel pump. We connected a fuel injector noid light to prove that the fuel
injectors were indeed working. Fuel pressure and volume were tested by hooking
up a fuel pressure gauge to the fuel line. A scan of the vehicle's computer
did not reveal any abnormalities in the datastream. Seven history codes were
stored related to Oxygen sensor activity and cylinder misfiring. These codes
seemed attributed to the current running state of the engine as opposed to
the actual cause.<br>
<br>
Suddenly, the car started and idled normally but could not be accelerated
without stalling. Now we were really scratching our heads. How could the
problem suddenly improve? How could the car be idling ok now? Could this
be an intermittent electrical problem? We tested the throttle position sensor
and mass airflow sensor and found them performing to normal voltage specifications.
<br>
<br>
Finally a break came in during a timing test. Timing was found to be off
by a large margin. We suspected that the timing belt may have jumped a tooth.
After removing the timing belt covers to access the belt and timing marks
the engine was found to be timed correctly. Again, the Lexus service manual
was in error. So much for the "relentless pursuit of perfection" Then again,
one could say that's why perfection is a relentless pursuit.<br>
<br>
A pattern in the cars performance was starting to emerge. The longer
the engine ran, the more its condition seemed to improve. Now the engine
was running well enough for a test drive. The car seemed much better but
was again getting low on fuel. Fuel was again added. The engine was running
well but would sometimes backfire if the engine were accelerated quickly.
One of our technicians then noticed something strange. When the car backfired
through the air cleaner, the puff of resulting smoke had the distinct smell
of diesel fuel. Our technician started to wonder if the car had been filled
with diesel or some sort of alternate fuel mixture. We then called and questioned
the customer further. The customer now added some important information.
When the car broke down on the highway the driver thought it might be out
of gas since the gauge was so low. The customer's roadside assistance plan
sent out a tow truck. The tow truck driver agreed that the fuel level was
too low and added some fuel. Since the car still would not run, it was towed
in.<br>
<br>
We believe that this vehicle's initial problem was that it just simply,
ran out of gas. Secondly, the tow truck driver may have accidentally grabbed
the wrong fuel can, and, unknowingly added diesel fuel to the car's tank.
Now that the car would still not run, it was then presumed something major
was wrong and then towed to us. <br>
<br>
Undoubtedly, one of the worse problems to discover and cure can be a fuel
quality issue. Both the car's computer, and we as technicians, "presume"
that the fuel tank has gasoline in it. The biggest issue with fuel
quality, or fuel "types," is that they are one of the last things ever tested
or investigated providing they are even checked at all. All the tests technicians
perform are based on the fact that "known good fuel" is in the fuel tank
and the fuel lines. The service manual presumes this as well as does the
vehicle's electronics. A fuel injector has no way of telling you its spraying
diesel, water or gasoline. <br>
<br>
Overall, nearly seven hours of diagnostic time was spent on this vehicle.
At one point, I overheard the customer say that it was: "Too bad the fuel
quality issue took so long to find." I replied to him that he was: "Lucky
it only took, seven hours." <br>
<br>
I can't begin to tell you how often I have heard of other shop owners complaining
that fuel quality issues can take 20 or more hours to find. Some technicians
will swap out all the sensors and computers one at a time trying to resolve
an engine running problem that routine tests can't find. One case I heard
of resulted in nearly 40 hours of labor. <br>
<br>
In the end, the more fuel we added the better the Toyota ran. After
adding a final 10 gallons of gasoline, the vehicle ran good enough to return
to the customer.<br>
<br>
Fuel type and quality issues are never the easiest problems to find. Sometimes
all it takes is a technician with a hunch and a keen sense of smell to find
these illusive problems. In addition, getting as much information out of
the customer can also be critical to a speedy resolve. <br>
<br>
Good luck in your future diagnostic dilemmas.<br>
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