On 9/16/2011 6:08 PM, Douglas Braun wrote:
> I bet that over the decades, at least 50% of all coil replacements actually
> replaced a perfectly good coil, with no effect on the car's operation.
>
>
There's a long tradition in this country of replacing parts until the
problem is fixed. In the case of hobbyist mechanics, that's sometimes
the only process possible, because they lack the necessary diagnostic
equipment, but most people would be surprised at the number of shops in
older times which allowed line mechanics without the requisite skills to
take jobs for which they did not have the training. In the `80s, I
worked in a shop that had eight mechanics, four of whom did not know how
to read the results from the Sun oscilloscope, and yet, all were
entitled to do tune-ups.
My favorite story along these lines was a kid given a truck with a bad
miss to diagnose. He changed the spark plugs and then dutifully hooked
up the `scope, peered at it a while, pronounced it a mystery and sent
the truck on its way. This was a Tuesday. On Friday evening after
work, he was having a bash at his house and had gone to the grocery
store for a couple of cases of beer. As he was leaving the store he saw
the truck idling in the parking lot and thought, "gee, that looks like
the..." and as he stepped off the curb, the truck exploded in flames.
(Later, he admitted to me that in that instant, he also thought, "oops.")
It was towed to us over the weekend, and the interior looked like a
Salvador Dali painting--headliner melting and hanging in drips, the
steering wheel twisted and melted, etc. The catalytic converter had
overheated and burst open. So, off it went to the body shop. When it
was returned, it was given to the same kid to replace the damaged
converter, which he did, and then started to park the car in the
"finished" lot. I went over to him and said, "whoa, whoa, whoa! You're
gonna send this thing out with the same problem that caused the damned
thing to explode? Go get the `scope." Hooked it up, put it in parade
mode and the problem was as obvious as the nose on one's face--only two
ignition traces, so I stopped the engine, pulled off the distributor
cap, and there were a couple of huge cracks and and carbon tracks
inside, the reason why it was firing on only two cylinders, and the
ostensible reason why the converter had overloaded on raw fuel,
overheated and blew up.
Now, without the `scope, some mechanics would do the visual inspection
that might have found the problem, but, the shop mandate was that
ignition diagnosis (and tune-ups) required use of the oscilloscope.
Good policy intended to help make proper diagnoses, but, worse than
useless if the mechanic couldn't read and interpret the results.
Ultimately, good diagnostic ability and information is the only way to
reduce the tendency to swap parts haphazardly.
Cheers.
--
Michael Porter
Roswell, NM
Never let anyone drive you crazy when you know it's within walking distance....
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