Sunday, December 17, 2017 Detailed Auto Topics
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mark twain-  

Mark Twain once wrote, "It ain't what you don't know that gets you into trouble. It's what you know for sure that just ain't so." Much common knowledge about vehicles falls into this category.

Many of the thing's folks accept as real, do cause a lot of the problems that they have. Making it worse, vehicles have changed a great deal and many things that may have been so at one time, no longer are.

Here's a short list of things that just ain't so with cars, with their origin and today's facts

 Thought: When a vehicle doesn't start, pumping the accelerator may help.

Origin: When vehicles had carburetors, pushing the gas pedal added fuel to the engine. This could help, especially if the choke did not work or the engine was cold.

Today: Pressing the accelerator on a modern vehicle does not affect the engine. Most vehicles have electronic throttle bodies and pressing the accelerator only work sensors, which is ignored by the engine computer.

Running a tank low on fuel may damage the fuel pump

  Thought: Running a fuel tank low is okay, no need to fill the fuel tank until it is empty.

Origin: Mechanical fuel pumps were mounted outside the engine and cooled by air flow. They operated at very low pressure and running out of fuel did no damage.

Today: Fuel pumps are mounted in the tank and operate at very high pressure. The fuel is used to cool the pump and provide needed head pressure. Running the tank to empty can damage an expensive fuel pump.

  Thought: Replacing the air filter will increase fuel mileage.

Origin: This is advertising rhetoric designed to increase filter sales.

Today: Engines match fuel to air flow. If air flow is decreased, the fuel added is proportionately decreased. This is true with a carburetor or an injector. Replacing a dirty air filter may increase power output, but it will NOT increase fuel mileage.

  Thought: Having a tune-up should fix a rough idle, poor fuel mileage or running problems.

Origin: Points, plugs and condensers in older vehicles wore out regularly. Performance, idle quality and fuel mileage would fall off and was corrected by a "tune-up."

Today: The engine computer controls ignition, timing, idle and engine performance, based on information from sensors. As spark plugs wear, the computer increases duty-cycle to the coils and performance stays the same. A tune-up will not cure a problem, but prevents failure of other more expensive parts, like coils and modules. Rough idle, low mileage and performance issues are symptoms of sensor or other failures and must be diagnosed to correct.

  Thought: A machine can tell you what is wrong with a vehicle.

Origin: Advertising rhetoric used to sell services. Several smaller pieces of equipment, such as an oscilloscope, vacuum gauge, timing light and dwell-meters were combined in a large cabinet. Mass-merchandisers often bought these and advertised them heavily.

Today: As in the past, no machine tells what is wrong. Curing problems often begins with scan tools retrieving diagnostic trouble codes or DTC. A technician applies their knowledge and several pieces of equipment to test the possible components that could set the DTC.

  Thought: Tires should be balanced every time they are rotated.

Origin: Advertising rhetoric designed to increase the profit margin of shops.

Today: Tires wear evenly around their perimeter, much like stock being turned-down in a lathe. The balance will not change unless the weights come off or move. If the proper wheel weights are used initially, balance should last the life of the tire.





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