Once upon a time there was an emergency room nurse who worked the midnight
shift. Every now and then, on her way home, her car would die. It always
happened after she had traveled far enough from the hospital to be truly
stranded. And since it happened late at night, it always left her terrified for
her life. But, fortunately the car never left her stranded. It always restarted
right away and got her home. It would happen only once.
Maybe it was the fact that she worked in the emergency ward. She had terrible
visions of being mugged by Jack the Ripper. Maybe it was her job that made her
think this way, after seeing so many gunshot wounds and huge knives sticking out
of bleeding bodies. She feared someone was making her car die, since it always
happened just about the same distance from the hospital.
To make matters worse, she had taken the car to just about every shop in town
and no one could find her problem. Various mechanics had already replaced the
computer twice and every sensor at least once _ some several times. A couple of
new distributor caps, rotors, ignition wires, ignition modules, fuel pumps, and
a multitude of fuel filters had been installed. She had already sunk a bundle
into the car in an effort to fix the problem.
Still, the problem remained. The car would just die and drift to the side of the
road. Not every night, just sometimes. And after she sat for a few moments in a
panic with her heart racing, the car would always restart, as if it was haunted.
Funny, it seemed as if nobody wanted to believe her. All the mechanics who
worked on her car treated her like she was crazy. They would keep the car for a
few days, even a week and never have it die for them. Maybe she was crazy, or at
least she began to doubt her own sanity. Then the car would do it again and she
would once more have the fright of her life.
One of the other nurses at the hospital overheard her talking about her car's
dilemma and suggested a mechanic who specialized in hard-to-find drivability
problems. In desperation, she called up and made an appointment to have Vic look
at her car. When she told her story, Vic responded with assurance that he would
be able to fix the car _ "once and for all." She wanted to believe him, but had
already been ripped-off by so many shops before.
But then he did something different. He told her that he would be connecting a
device to her car that would be capable of recording the problem. She was to
continue to drive the car and when it stalled, push a button on what Vic called
his "flight recorder." He then connected a funny-looking box up to her car and
gave her detailed instructions on what she was supposed to do when it happened.
He told her to go about her business as usual, but at the moment it happened,
she was to quickly press the big, red button on the recorder and keep her foot
steady on the gas pedal. He said that if she pumped the gas pedal, or brake, it
would make it harder to find out what went wrong. "Giving it gas makes a whole
bunch of other things change and it makes it harder to spot the real problem."
She said she would do her best.
On her way home the very next night it happened again. Just as instructed, she
pressed the big, red button on Vic's flight recorder. As always, she freaked out
and steered the dying car to the roadside edge. As always, it restarted with
just a twist of the key. She could hardly wait until the next day so Vic could
find the problem and fix her car.
Much to her surprise, Vic wasn't even interested in her story. He told her to go
to the waiting room and let him examine what had been captured on his flight
recorder. A few minutes later he came into the waiting room and said, "The
others may not believe you, but I do. I saw your car die on the flight recorder.
It definitely died... and you were going about 45 mph when it happened."
She felt her face flush as she breathed a big sigh of relief. For the first
time, she felt taken care of. Vic told her to take the car home and make arrangements to drop it off for further, more thorough examination. She offered
to call a friend and leave it. Vic said OK.
Carefully, Vic poured over the data captured from her dying car. In much the
same way that an airplane flight recorder remembers what happened before the
plane crashes, his recorder remembered what was happening when her car died. It
was all there; he just had to make some sense of it.
Because there is so much different information to examine, Vic copied the
readings from the recorder onto a sheet of paper. He especially wanted to see
what happened when she pushed the button. Sure enough, at the second before she
pressed the button, the engine dropped 400 rpm. In the next moment it went back
up to 2400 rpm and a couple of seconds later it dropped to 500 rpm. Then in the
next second it would come back to life and then die again. This time it would
not recover.
Frame by frame he examined the data. One thing seemed obvious: it was somehow
related to the fuel system. Each time it faltered, the mixture went totally
lean. Each time it recovered, the mixture went rich. It was just like it was
running out of gas. Or was it? He immediately thought of the fuel pump. But
could a failing pump turn the fuel off in one second and back on in the next?
No. If the pump were to die it would take more than a second for the engine to
run out of fuel. It would be much more gradual.
Fuel filter? No, he reasoned. Fuel filters don't come and go. They just plug up
and stay that way. Fuel filters never unplug. Ditto for a catalytic converter.
And he knew the ignition module wasn't at fault because he watched the engine
lose rpm's over a time span of a couple of minutes. If the module were to fail,
the rpm's would just drop to zero _ all at once.
What about the injector? Could it be sticking? Maybe it sticks shut every now
and then. Maybe the injector has a weak spring and sometimes just decides not to
open and stays shut. But why only late at night? Why does it work fine once it
stalls? Why couldn't anyone else witness it? He thought about the other repair
orders, each full of attempted repairs and each with a hefty price tag.
No one had replaced the injector on this 4-cylinder throttle-body fuel injected
car. Still, the fact that it only happened late at night nagged at him. After
studying the recorded data, Vic only had an educated hunch. Armed with his best
guesses, he was ready to look at her car and begin checking out his theories.
The first thing he wanted to examine was the injector.
Remember, at this point he had not even lifted the hood of the car. Now he did
so, and removed the air filter to get a better view of the injector. "So far, so
good," he thought as he reached for the injector harness plug. He was about to
connect his injector tester to the single throttle body injector when he saw it.
It was grossly green, slimy and looked very nasty. The injector connector was
being eaten up by what looked like green fungus!
"That's why it only happened late at night! The humidity in the air was enough
to make this connection have too much resistance. And when the car died and sat
for a few moments, the heat from the engine would dry it out, giving it a good
connection for the rest of the way home," Vic told her.
He carefully cleaned and tightened the injector connector and fixed the nurse's
car without replacing a single part. And the nurse lived happily ever after!
