Driver Guide To A Car Engine Operation

Your engine is one of the most complex assemblies under the hood (second only to the transmission). It is filled with moving parts that work together seamlessly to propel your vehicle down the road. But few people are familiar with the process that makes this possible.

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Below, we’ll take you on a brief tour of your car’s engine. You’ll learn about the components that play key roles in its operation. We’ll describe what these parts do so you’ll understand how they contribute to the performance of the assembly. You’ll also begin to appreciate why certain problems surface as the components wear down over time.

Major Components Of Your Engine

The size and power of the assembly is dictated by the number of pistons. Small passenger vehicles may only have four. Sedans may have six, and larger automobiles and performance vehicles often have eight. Some trucks come with more. Each piston is contained within a cylinder. The top section of the cylinder is called the combustion chamber. The piston rises up and down according to a precisely-timed 4-stroke combustion cycle (described in more detail in the following section).

Each of the engine’s pistons are attached to a shared component called the crankshaft. As the pistons rise and fall within their respective cylinders, the crankshaft turns on its axis. It rotation moves your vehicle.

Atop each cylinder is found an intake valve and an exhaust. These open and close to help regulate the flow of fuel, air, and exhaust. The valves are connected to camshafts, which, in turn, are connected to rocker arms, lifters, and other parts. These comprise your car’s valvetrain.

Together, the pistons, crankshaft, and valvetrain control the timing of your engine’s 4-stroke combustion cycle. This cycle occurs inside each cylinder, and is the most important task for which your engine was designed.

The 4-Stroke Combustion Cycle

Recall that fuel enters the cylinders through the intake valves. Also, recall that the up-and-down movement of the pistons causes the crankshaft to rotate, which moves your car. What follows is a step-by-step description of this process. There are four distinct strokes: intake, compression, power, and exhaust.

The intake stroke occurs when a camshaft forces the intake valve open. As it opens, the piston descends within the cylinder. Air and fuel fill the chamber, after which the intake valve closes.

The compression stroke begins when the piston starts to rise from the bottom of the cylinder. With the intake valve sealed, the air-fuel mixture in the combustion chamber starts to compress. By the time the piston reaches the top of its path, the mixture will have been compressed to approximately 10 percent of its beginning volume.

During the power stroke, a spark plug at the top of the cylinder ignites the compressed air-fuel mixture. This produces a rapid expansion of gases. The vapors push the piston downward in the cylinder, causing the crankshaft to rotate.

The exhaust stroke is the last stroke in the cycle. At this point, the piston is at the bottom of the cylinder. The exhaust valve opens, and the piston begins its ascent again. This pushes the vapors in the combustion chamber out of the cylinder via the open valve. Once the gases have been expelled from the chamber, the exhaust valve closes, and the combustion cycle begins anew.

How To Extend Your Engine’s Life

The components mentioned thus far (pistons, valves, camshafts, crankshaft, etc.) will eventually wear out. Under normal driving conditions, a new engine can be expected to last 100,000 miles or more before it needs to be overhauled or replaced. You can prolong its life by keeping the oil level replenished, and changing the oil according to the service interval recommended by your owner’s manual.

Also, make sure to have the timing belt replaced every 60,000 miles. If it breaks while your engine is in operation, it can cause expensive damage to the valves and pistons.

Being familiar with your engine and how it operates is useful for troubleshooting sporadic issues. While repairing engine problems may be beyond your skill and experience, knowing what caused the problems in the first place can prove invaluable.

Identifying The Root Cause Of Engine Noise

Cars that were built a generation ago had a relatively simple design compared to those rolling off factory floors today. The engine, in particular, had fewer moving parts. Vehicles today are equipped with engines that are far more powerful and efficient. They are also much more complex, which means a greater number of things can go wrong.

In most cases, your vehicle will issue warning signs that indicate there is a problem with the engine. For example, the “check engine” light will usually go on, the assembly might misfire during acceleration, or a rough idle may become increasingly pronounced as the underlying issue worsens over time. Your engine might also make uncharacteristic sounds. When this happens, it is important to know how to troubleshoot the root cause, so you can address it. This article will offer a quick guide to doing so.

Tapping

If you hear tapping from your engine, there’s a good chance the oil level is low. Motor oil is essential to the assembly’s smooth operation because it provides lubrication for the moving parts. Without it, components will begin to make contact with each other.

One of the reasons this occurs is because of thermal expansion. As heat surrounding the engine rises, the metal from which the moving parts are designed expand. This reduces the amount of clearance that exists between them. If the oil level is low, there will be too little lubrication, and tapping can result. Replenish the oil level as soon as possible to avoid damage.

Knocking

This sound usually indicates that the fuel inside one or more cylinders is exploding out of sync with the spark generated by the spark plug. It is commonly called “spark knock,” and occurs when excess heat builds up in the cylinder. Because the timing of the cylinder’s valves and piston are thrown off, they collide. Both may become damaged.

Spark knock can occur for a number of reasons, including an excessive compression ratio in the cylinder and a malfunctioning exhaust gas recirculation (EGR) system. An overheating engine combined with low-octane fuel can also cause the problem.

You might also hear a deep knocking noise that sounds as if something is being struck by a hammer. This is typically caused by rod bearings that have become severely worn. When a bearing fails, your engine may sustain damage.

Squeaking

This noise can be generated by an assortment of small parts throughout the engine. A common cause is that one or more of the pulleys around which the timing belt moves has become loose. You can check the pulleys easily by turning the engine off, lifting the hood, and feeling for tension in the belt. If there is inadequate tension, check the individual pulleys, and replace the one that is about to fail.

If the tension in the timing belt is fine, check the pulleys near other components, such as the A/C’s compressor and alternator. When they come loose, they can make the same squeaking sound.

Shaking

At times, you may hear a knock-like shaking sound coming from the bottom part of the engine. This can be caused by something simple, such as carbon deposits having formed on one or more pistons. Such deposits often develop over time as a result of the combustion cycle. Unfortunately, fixing this problem requires taking the engine apart, a job that is usually expensive due to the labor involved.

Some of the noises described above may occur in the absence of an obvious reason. Avoid neglecting the noise. If you suspect there is a problem in your engine, have a technician perform a test. Even though doing so costs money, the investment is worthwhile since ignoring a strange sound can lead to a costly engine overhaul down the road.

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