The auto newsgroups need a FAQ like the sci.electronics.repair FAQ.

I've seen so many so amateur mechanics who are so clueless about
troubleshooting procedure that it isn't funny.  For example, I once
had a room-mate who's car had died and he was walking to/from work for
a week.  He had a friend over who was in the process of ripping the
dash apart and I asked him what he'd checked so far.  He was starting
at the ignition switch.  I joked that he should check if there was air
in the tires, and f.ck me drunk, he was about to follow my advice.

I took over and started right at the ignition system.  Pulled a wire,
had him crank the engine and there was a nice fat spark.  Next:  fuel
system.  Asked if there was gas in the car.  They didn't know, the
fuel guage was broken.  I pulled the gas cap and rocked the car and
didn't hear any splashing.  The car had run out of gas right at the
moment it was parked and couldn't start again.

People need to learn some trouble shooting skills before they start
asking questions like "my car won't start;  what part should I replace?"

I've been guilty of the same thing.  I had an acura integra that
wouldn't start.  No spark.  Checked the coil and it measured good.
Replaced the ignitor.  Still no spark.  Was about to replace the
output transister of the ECU, but was so impressed with its internal
aerospace quality, that I decided to keep looking elsewhere.  Put the
ECU->ignitor signal on an osciloscope and saw a pulse.  Replaced the
coil that had measured good.  Fixed the problem and only wasted $90
which was more than a mechanic would have charged to diagnose and
repair it in the first place.