The 4-stroke combustion process (intake, compression, power, and exhaust) normally occurs smoothly. The pistons, spark plugs, fuel injectors, and other components work like a well-oiled machine. Pressure builds within the combustion chamber until the air-fuel mixture contained within it is ignited by the spark plug. That’s what propels your vehicle forward. When you hear a knocking sound as you accelerate, especially during heavy load, that means there is something wrong with your engine. This is called spark knock. And it can lead to expensive damage.

In this article, I’ll explain what is happening inside your engine to produce the knocking or pinging sound. We will explore some options and provide some clues to the root problems.

What Is Spark Knock?

The knocking sound is due to the fuel within your vehicle’s combustion chamber detonating. Rather than burning cleanly, it explodes under load, over and over. This happens when the heat and pressure contained in the chamber is erratic. It is not being controlled properly, and the excess heat and pressure is igniting the gas.

You might not immediately notice a change in the performance or output of your car engine. However, over time, spark knock can lead to cracked rod bearings (from the pistons), broken rings, and head gasket problems. Each of these problems can be expensive to repair.

Reasons Knocking Can Happen

So, why does detonation happen? It can occur when your car’s exhaust gas recirculation (EGR) system malfunctions. The EGR valve is tasked with opening when you’re pushing your engine under heavy load (for example, if you’re towing something up a hill). By opening, it allows excess exhaust to flow out of the combustion chamber, lowering the temperature. If the EGR fails, this process cannot happen.

Detonation can also happen if your car’s knock sensor malfunctions. This sensor is supposed to identify situations in which the fuel is igniting erratically. It then tells your car’s computer to change the ignition timing in order to compensate. A failed sensor prevents this from occurring.

With many later model cars, detonation can be the result of carbon buildup. This will occur when their is a build up of carbon inside the pistons combustion chamber. Fortunately, this problem is simple to resolve; most mechanics will flush the injectors and the combustion chamber with a special detergent that clears away the carbon deposits.

Lower octane value gas can be a main cause of detonation. Some gas station owners label their pumps with “87″ when the octane is actually lower. Try filling your tank with a premium grade fuel from a respected brand (for example, Chevron).

If you hear knocking when your engine is under heavy load, take your vehicle to an experienced mechanic as soon as possible. He’ll have the necessary equipment to test your engine and identify the root cause of the fuel detonation. If you ignore the problem, you could be setting yourself up for expensive repairs in the future.

Tags: Autos, car, Car Engine, Car Maintenance, car repair, Car Tips, cars, Vehicle

This entry was posted on Sunday, December 20th, 2009 at 7:30 am and is filed under General. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.