THE CAR NAIRA BLOG

The purge valve is the part of the vehicle Evaporative Emission Control (EVAP) system. The EVAP system prevents fuel vapours in the fuel tank from escaping into the atmosphere. The EVAP system traps fuel vapours from the fuel tank and temporarily stores them in the charcoal canister. A purge valve solenoid EVAP system diagram When the engine is running under certain conditions, the fuel vapours are purged from the canister and burned inside the engine. The purge valve precisely controls the amount of fuel vapor that is purged from the charcoal canister. In modern cars, the purge valve is an electrically-operated solenoid, that is controlled by the engine computer. When the engine is off, the purge valve is closed. When the engine is running and fully warmed up, the engine computer gradually opens the purge valve to allow some amount of fuel vapours to be moved from the charcoal canister and burned in the engine. The purge flow is monitored by a number of sensors. If the purge flow is l...

Most cars have two control arms in the front suspension. Often they are called lower control arms. Some cars and many trucks have four control arms, two upper and two lower arms. Upper and lower control arms A control arm connects the frame or body of a car to the assembly that holds a front wheel. This assembly is called a steering knuckle. Car schematic showing lower control arms Control arms are connected to the frame or body of a car through flexible rubber bushings, called control arm bushings. This allows a control arm to swing up and down as front wheels roll over bumps and potholes. The outer end of a control arm has a ball joint. In some cars, a ball joint is bolted to or pressed into the control arm and can be replaced separately. In others, a ball joint comes with a control arm as one piece. Control arms have a very important role holding both front wheels on the road. If a control arm is excessively worn, damaged or bent, the vehicle is NOT SAFE to drive. Control Arm Proble...

Brake light switch is a small device attached to the brake pedal mechanism. The brake light switch plays an important role in a modern car.  A brake light switch Many vehicle systems including Push-Button start, Antilock Brakes and Vehicle Stability Control cannot operate if a brake light switch is not working properly. The brake light switch serves two major functions. First, it turns on the brake lights when a driver presses the brake pedal. Second, it sends the signal to the vehicle computer that brakes are applied. A car with a faulty brake light switch is UNSAFE to drive. Illustration showing the relationship between a brake light (stop lamp) switch and the brake pedal In most cars, the brake light switch is installed right above the brake pedal. Inside, it has a one- or two-way electric switch. The most common symptom of a faulty brake light switch is when brake lights don't come on or stay on all the time. Brake Light Switch Problems A faulty brake light switch can cause man...

In a car engine, an intake manifold distributes the air flow evenly between the cylinders. In many modern cars, intake manifolds is made of plastic as a compromise between weight and cost.  Often an intake manifold holds the throttle valve (throttle body) and some other components. An intake manifold consists of the plenum and runners. In some V6, V8, V10, V12 and W12 engines, an intake manifold can be made of several separate sections or parts. An intake manifold The intake air flows through the air filter, intake boot (snorkel), then through the throttle body, into the plenum, then through the runners and into the cylinders.  Path of airflow into an engine In modern cars, the engine idle speed is also controlled by the throttle body: at idle, it opens at a very small angle. Because the throttle body is almost closed when the engine runs at idle, there is vacuum inside the intake manifold. If there is a vacuum leak somewhere in the manifold, the engine will run rough (unstabl...

An ignition coil is a part of the vehicle's ignition system. It converts 12V battery power into high voltage in order to create a spark at a spark plug. The spark ignites the air/fuel mixture in the engine cylinders. An ignition coil cut-out and a plug Most of the modern cars have one ignition coil per cylinder. Often, an ignition coil is installed right over the spark plug. This setup is called coil-on-plug. It is more popular in modern engines. On-plug coil In some cars, ignition coils for all cylinders are combined into one coil pack. In older cars with a distributor, a single coil is used for all cylinders. See this example of a single ignition coil in a Volkswagen air-cooled engine. A coil pack in a Volkswagen Ignition coil problems Ignition coils are common to fail in many cars. Symptoms of a bad ignition coil include engine shaking, sputtering and lack of power (misfiring). The Check Engine light will flash repeatedly or stay on solid on the dash. In cars with a single ignit...

Fuses are safety devices that protect electric circuits in a car from excessive current (overloading). Without a fuse, an overloaded wire could melt or catch a fire. Each circuit has its own fuse. Several larger fuses with high Amp rating protect multiple or high-current circuits, such as electric power steering or radiator fan circuits. There is also at least one main fuse. Often the main and high-Amp fuses are installed closer to the battery.  Fuse box Modern cars have at least two fuse boxes. In most cars, one fuse box is installed under the hood; the other is located inside the car. A fuse box in the cabin of a car When any electrical component in a car doesn't work, the fist step is to check the fuse that protects the circuit with this component. You can find the fuse map in the owner's manual, or on the fuse box cover. In many cars there is a tool to pull the fuses that might be located in the fuse box or in the fuse box cover (if the local electrical technicians haven...

All modern cars have disc brakes on front wheels and disc or drum brakes on the rear axle. How do disc brakes work? The main component of the disc brake setup is a brake calliper. The hydraulic piston(s) inside the calliper can apply clamping force to the brake disc using two brake pads. The clamping force can slow down or stop the rotation of the disc and the wheel. A disc brake assembly Passenger cars, SUVs and pickup trucks on the road today have a hydraulic braking system filled with brake fluid. When the driver presses the brake pedal, it pushes the piston inside the brake master cylinder that creates pressure within the hydraulic braking system. The brake fluid transfers the pressure to the brake callipers that apply brakes to the wheels.  How a disc brakes works Parts of a Disc Brake Parts of a disc brake assembly Brake Disc (rotor):  The brake disc (rotor) is mounted on the hub and rotates together with the wheel. During braking, kinetic energy of the vehicle converts ...

Many modern cars have a battery current sensor. It might also be called a battery management or monitor sensor, or simply battery sensor. Typically, a battery sensor is installed on the negative battery terminal or on the cable. It might be installed on the positive terminal. Some cars have two sensors, one on each terminal.   A BMW battery sensor How the battery sensor works: it measures the current to and from the battery. It may also monitor the voltage, state of charge and state of health of the battery (aging). In some cars, it even measures the temperature of the battery. The vehicle computer (Body control module BCM or Powertrain control module PCM) uses these inputs to precisely adjust the charging system voltage, idle speed and other parameters for better fuel efficiency and longer battery life. This system is called Power or Battery Management System or BMS. If the system detects that the battery is getting weak, it may turn off some electrical accessories (load shedding)...

An alternator is a generator of electric power in a car and is a major component of the vehicle's charging system. All cars with an internal combustion engine except for some hybrids have an alternator. When an engine is running, the alternator charges the battery and supplies additional electric power for the vehicle electrical systems. It is bolted to the engine and is driven by a serpentine belt (drive belt). An alternator An alternator is a maintenance-free unit. It can last for up to 10-15 years without any repairs. If an alternator fails, the car may still run for a short time on battery power (older cars). However, the engine will stall as soon as the battery charge is depleted.  Symptoms of alternator problems The most common symptom of a problem with your vehicle's charging system is a battery-shaped warning light (in the photo) or the "CHARGE" icon that comes on while driving. Normally this warning light should come on when you turn the ignition, but should ...