The knock sensor sends voltage signals back to the ECU, which uses those to determine if the timing for the engine needs to be retarded, before damaging pre-detonation occurs.

Valve covers are designed to take the hassle out of adjusting valves somewhat regularly. They come off by removing just a few bolts and go back on with similar ease.

Sometimes this can be the hardest part of doing an oil change, if you don't have a wrench that's up to the challenge. You can also use penetrating lubricant on the bolt and let it sit for a little while.

When the engine is turned off, you can use the dipstick to see if the oil is full enough, or if you need to add a quart or two. You'll need a rag or paper towel to clean the dipstick off to get an accurate reading, though.

It's amazing to think the spark plugs in your engine are constantly producing sparks to trigger mini explosions in the cylinders, which then turn the wheels.

Valves open and close passageways. In this case, the valve opens and closes the pathway in the cylinder head that connects to the exhaust manifold.

Piston seals are usually made of rubber or a similar substance, so they create an airtight seal that won't let exhaust gases or the air and fuel mix to seep out in the least.

The air temperature sensor gives feedback to the ECU, since this information can affect how much fuel should be sprayed by the injectors. The colder the air, the more oxygen-rich it is.

With all the force exerted on the piston and connecting rod each time the air and fuel ignite, the gudgeon pin has to be strong and durable, otherwise the engine would fail quickly.

The fuel injector has an incredibly precise nozzle, so the car's ECU can regulate with precision how much fuel should make its way into the cylinders at any given moment.

Sometimes called a crank sensor, this sensor is vital in managing the engine's timing, which is especially important in a variable valve timing setup.

Just how hard replacing the spark plug tube gaskets is really depends on the engine, just like so many other components.

If you look at the underside of your engine oil cap, there's a rubber or silicone seal that should create a tight seal. If that fails, you could conceivably replace it, but you might find it easier to just buy a new cap.

To help starting the car up when the engine is cold, some designs use a pipe that's triggered by the temperature of the coolant and/or a timer circuit.

You might hear valve lifters referred to as a tappet or lash adjuster, but it's the same thing. Just remember that solid valve lifters need to be adjusted periodically.

Most people don't think at all about the valve springs in their engine, even though this part is absolutely essential for proper compression.

Idler pulleys keep the belts that drive the alternator, water pump, power steering pump and AC compressor at the proper tension and moving at the right points around the engine compartment.

Not only do you need a torque wrench to tighten the bolts enough, you should always follow the manufacturer's recommendation for the tightening pattern.

While the camshaft triggers the motions of the valves, it's the actual valves that either let the gases flow in the engine or sit.

The piston ring is usually made of rubber or a similar substance and it sits in a groove that runs around the sides of the piston, forming an airtight seal that the air/fuel mix and exhaust gases shouldn't flow past.

It might sound simple, but the water outlet on your car's engine is essentially a pipe that connects to the water jacket, letting hot coolant flow out of the engine and toward the rest of the cooling system, namely the radiator.

The purpose of the connecting rod bushing is to reduce vibrations in the engine, but they're made of a durable metal, so they don't dampen as much as rubber bushings would.

The camshaft knock pin fits on the end of the camshaft. Not only does it hold the camshaft sprocket where it should go, the pin lines up the two parts correctly.

Replacing valve seals is actually a pretty easy job, but it is a little on the tedious side. If you must pass emissions in your area, doing this will be essential.

At the end of the camshafts in a car's cylinder head is a rubber seal, designed to keep the oil inside the engine. Normally these last a long time, but in older engines the seal may fail.

Even though they're small, the main bearings have a difficult and critical job, considering the crankshaft is converting the up-and-down forces of the pistons into a rotational force.

Not every engine has torque-to-yield head bolts, but just about every automaker uses them when the cylinder head is made of aluminum.

The valve cover is located at the top of the cylinder head, making it a likely source of the leak. Of course, the oil cap is another potential origin.

The valve spring, keeper and retainer work together to create a constant amount of pressure, which snaps the valve closed tightly.

Essentially, a rocker arm is an oscillating lever that's actuated by a pushrod, which is actuated by the lobes on the camshaft.

Engines have plenty of moving parts, and that means vibrations are inevitable. The valve guide is the cylinder that the valve moves back and forth in. This bushing just tries to reduce vibrations created by that movement.

The valves in a non-interference engine never occupy any space the pistons do, even at different times. That means they're never at risk of colliding, which can damage the pistons as well as the valves.

Sometimes called the harmonic balance wheel or crankshaft sheave, is an essential part of the engine's timing system.

Camshafts aren't perfectly straight shafts, otherwise the engine wouldn't run properly. They contain uneven lobes that determine when, how much and for how long the valves open.

The air temperature sensor sits in the air intake, gathering data that helps the ECU measure how much gas should be injected into the cylinders. The colder the air, the more oxygen atoms in each cubic inch of it.