There are a lot of rules of thumb, superstitions and rituals in the car guy world (cue Stevie Wonder). A lot of things are done because that is the way they have been done or should be done. I’m sure many of these are based on real-world experience. Some may not be.
Rules of thumb (heuristics, if you are in management) such as “80% of all ignition problems are fuel related” and the converse “80% of all fuel problems are ignition related”. Pretty much true, I’ve been bitten by this one more than once – fiddling around with carb floats multiple times due to a bad coil.
Superstitions like “never putting a battery directly on a concrete floor as it will drain the battery”. This one gets argued time and again, but most of us end up putting a piece of wood underneath a pulled battery – just in case.
Then there are the rituals. These come about due to the fact that “it worked last time” or “I’ve always heard that you have to….”. Many of these work for a good reason – they just work. For example, there is always “that guy” who will try to swap a clutch in a Datsun roadster without pulling the motor and tranny as a unit. Usually this person has been told several times about the proper rites and rituals, but somehow that just doesn’t sink in and they have to learn the hard way – I’ve seen frames cut to try to avoid pulling the engine!
One of my rituals is the preparation for a Smog Test. I haven’t had to do this in a while – due to owning older cars that are exempt, and also from living where smog checks are not required. But, I live in Portland now and most of the I-5 corridor requires them. I got the notice in the mail recently that my ’85 Volvo wagon was due for a check-up. I bought it as a non-runner about 10 months ago and put a “fresh” 175,000-mile engine into the 275,000-mile car. The engine had been sitting in a salvage yard for about 3 years and looked good, but you never know. The post-swap car drove fine and gave no signs of “gross polluting”, but you never know… Ritual to the rescue!
The first part is to change the oil. The idea is that the old oil contains contaminants that might effect the smog test – new oil – no bad juju.
Then comes the Italian Tune-Up. Wikipedia claims that it involves running the engine at high-revs for 20-30 minutes but implies that this is done while the car is stationary – some sort of a Mercedes diesel ritual. I’ve always thought of it as “blowing out the carbon by driving the snot out of a car” for 20-30 minutes. Most people under-rev their cars, shifting gears long before they even get into the power band. The thought is that this gums up the works and that a proper cleansing is in order.
I had a friend in college who was convinced that something was dreadfully wrong with her new-to-her Honda as it bucked and wheezed when she drove it. I took it for a spin and couldn’t find anything wrong. She then took me for a drive, shifting every gear at 1,000 rpm and it did buck and wheeze just like she said. The redline on this poor thing was at least 6,500 and it had never been near it. I took it for a 20-minute “tuning session”, bouncing off the rev-limiter in the higher gears, warming up the tires and brakes, and checking out the “handling”. Not quite doughnuts and hand-brake turns, but the car was much happier for it. Giving off that “tick, tick, tick” noise of contentment as it cooled down after the workout.
So I took the old girl (we’re back talking about the Volvo 245) out for a spirited drive in the rain on the way to the testing station. As spirited as you can get an aerodynamic-as-a-brick, 3,000-lb, door-handle-scraping-on-the-road-in-a-turn, wallow-box anyway. Great fun, and of course, due to all this hard work and attention to ritual – she passed the smog check with flying colors.