Thursday, 23 June 2016

Why does a car backfire?

Car backfire

Why does a car backfire?
Credit: Johner Images - Kohvakka, Kari Brand X Pictures Getty Images

Cars backfire for several reasons, including air and fuel mixing due to leaking hoses or other mechanical problems. Faulty spark plugs or wires can cause a car to backfire. It can also occur when shifting to a lower gear in a car with high horsepower. 

Backfire is a small explosion produced by a running engine outside the combustion chamber. When unburned fuel mixes with air, it can ignite when an intake valve opens. Visible flames may shoot from the car's exhaust pipe and cause a popping sound.
Backfire can result in a car losing power. The term comes from early guns, which were unreliable and sometimes fired from the back instead of from the muzzle. In common usage, the word also refers to something that causes an undesired outcome.


What problems can the check engine light possibly indicate?


A lit check engine light in a vehicle is indicative of one or more problems including faulty oxygen sensors, leaking hoses or manifolds, damaged fuel injector O-rings, a blown head gasket and a loose or damaged gas cap. A blinking check engine light indicates an emergency problem that requires repair.

Dealing with a check engine light on your vehicle’s dashboard can be frustrating. While the little light is meant to warn you of a problem – what the problem exactly is can be a mystery. Somewhere inside your vehicle, something happened to trigger the light.

Although you'll probably have to take your car to the shop to get the exact answer, there are a few things you can do immediately after seeing the "service engine soon" light turn on for the first time.

The most common cause of a lit check engine light is a faulty or loose oxygen sensor. The oxygen sensor measures the oxygen content of a vehicle's exhaust, allowing the computer to compensate with more or less fuel. A loose or missing gas cap is another common cause for a lit check engine light. After replacing or tightening the gas cap, it may take several trips to reset the check engine light.
A blinking check engine light is caused by major malfunctions such as unburned fuel entering the exhaust system or a blown gasket or piston. If the check engine light is blinking, pull over as soon as safely possible and do not drive the vehicle.
Accurately diagnose a check engine light by taking the vehicle to a professional mechanic or auto parts store that can read the code using a specialized device. Diagnostic code readers provide a series of digits and characters that can be used to interpret the exact cause of the lit check engine light.

You're driving along in your car or truck and suddenly a yellow light illuminates on your dash telling you to check or service your engine. If you're like most car owners, you have little idea about what that light is trying to tell you or exactly how you should react.

Call it the most misunderstood indicator on your dashboard, the "check engine" light can mean many different things, from a loose gas cap to a seriously misfiring engine.

"It doesn't mean you have to pull the car over to the side of the road and call a tow truck. It does mean you should get the car checked out as soon as possible," says Dave Cappert of the National Institute for Automotive Service Excellence, a Virginia-based organization that tests and certifies auto technicians.

Ignore the warning, and you could end up damaging expensive components. It also can be a sign that your car is getting poor fuel economy and emitting higher levels of pollutants.

What the light means
The "check engine" light is part of your car's so-called onboard diagnostics (OBD) system. Since the 1980s, computers increasingly have controlled and monitored vehicle performance, regulating such variables as engine speed (RPM), fuel mixture, and ignition timing. In some cars, the computer also tells the automatic transmission when to shift.

When it finds a problem in the electronic-control system that it can't correct, the computer turns on a yellow warning indicator that's labeled "check engine," "service engine soon" or "check powertrain." Or the light may be nothing more than a picture of an engine, known as the International Check Engine Symbol, perhaps with the word "Check." In addition to turning on the light, the computer stores a "trouble code" in its memory that identifies the source of the problem, such as a malfunctioning sensor or a misfiring engine. The code can be read with an electronic scan tool or a diagnostic computer, standard equipment in auto repair shops. There are also a number of relatively inexpensive code readers that are designed for do-it-yourselfers.

Manufacturers originally used the OBD system to help technicians pinpoint and troubleshoot malfunctions. But the systems now are required under federal laws governing automotive emissions. Although larger trucks have been exempt from the requirement, that quickly is changing.

"The 'check engine' light is reserved only for powertrain problems that could have an impact on the emissions systems," says John Van Gilder, General Motors' lead OBD development engineer.

Exactly what the OBD system looks for depends on the make, model and year. The original systems varied widely in their capabilities. Some did little more than check whether the various electronic sensors and actuators were hooked up and working.

Get your car checked out

Some also refer the check engine light to the service engine soon light and the maintenance required light.
If the check engine light turns on and you start noticing problems with your vehicle's performance, take it to an auto service shop right away. In some cases, a yellow check engine light may indicate that a problem exists, but it's not very urgent. Other times, a red check engine light or a blinking check engine light may occur. In those cases, the problem most likely requires immediate attention. In these cases, it could be a problem related to you car's emissions system or a costly repair like needing a new catalytic converter.
In some cases, it could take time for your mechanic to diagnose the problem. But they should tell you how long they think it will take and how much it will cost.


  • Q:

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    • Check your gas cap

      A missing or faulty gas cap can turn a check engine light on. The pressure inside your gas tank is thrown off-kilter when the gas cap is off or not secured properly. To your car's on-board diagnostic system, or OBD system, a change in pressure could indicate a leak in the emissions system, so the light is triggered to alert you to the problem. Replace the missing cap or tighten the existing one to see if the problem goes away. Give it at least a week. If the light stays on, head to the repair shop or dealership.

What does it mean when my car turns off while I am driving?

Car turns off while driving

CarsDirect identifies three of the most common problems that cause a car to switch off while a person is driving: broken or worn vacuum hoses, faults in the fuel intake system or an electrical wiring problem. Any one of these issues may cause a car to shut off randomly, but by following some basic troubleshooting steps, drivers might be able to pinpoint the source of the problem.

Vacuum hoses maintain the temperature and pressure around an engine. Over time, they become cracked and worn, which can cause the engine to stall. A vehicle's fuel intake system pumps fuel into the engine. If it gets clogged or starts to leak, an insufficient amount of fuel can cause the engine to shut off without warning. Finally, the vehicle's electrical system provides the spark necessary to ignite the fuel and power the car's engine. Faulty wiring can also cause vehicles to turn themselves off.
Sometimes, drivers can determine the source of the problem without a mechanic. They can check all the wiring and rubber hoses attached to the engine for leaks, cracks or other signs of extreme wear. They can also perform this check with the engine switched on to listen for the sounds of escaping air.

What does it mean when my car turns off while I am driving?