Each of the engine knock causes on the previous page has a specific cure, and most of these fixes are simple. However, it doesn't guarantee the knock will go away. It's easy to misdiagnose the cause of knock, and there might be more than one cause, so you might have to pay a visit to your mechanic. Also, some older cars are simply prone to engine knock, and might continue to ping away no matter what measures are taken [source: Allen]. Mike Allen, the automotive columnist at Popular Mechanics, says that an older car with a persistent ping is probably not in any immediate danger. But if you've only recently noticed the knock and think it's a new problem, or if the noise is simply unbearable, there are a few steps that can be taken.
First and foremost, try using higher quality fuel. Make sure you're buying fuel with an octane rating in accordance with your auto manufacturer's recommendation -- this information should be in the user manual or on a sticker near the car's gas cap. Most cars in the United States should be good with 87 octane fuel, but high-end and performance cars probably require a higher rating. The Federal Trade Commission suggests switching to a higher octane rating than recommended only if intended to alleviate knocking. If you suspect your car has old or bad gas, try adding an octane boost additive until you've run through a few fresh fill-ups. There are a few different types of detergents that can be added to the gasoline, such as fuel injector cleaner, which can help dirty combustion chambers as well as the injectors. Try running it through at least three full tanks of gasoline before evaluating the results [source: Allen]. And if these simple tricks don't help, try switching gasoline brands. Even if the above steps didn't appear to solve the problem, they certainly didn't hurt.
Decreasing the compression ratio can also help alleviate the causes of knock. The next potential culprit is dirty cylinders, and again, the plan is to try to flush them clean. Over time, carbon components that are present in all gasoline build up. Small deposits can compound over time, and higher compression often increases the formation of deposits, so the problem can quickly get worse. It's much easier to run a cleaning additive through the gasoline every now and then (at the manufacturer's recommended interval) to keep the cylinders reasonably clean, than it is to fiddle with compression and temperatures to accommodate existing deposits that will just get larger. There are a few different types of detergents that can be added to the gasoline, such as fuel injector cleaner, which can help dirty combustion chambers as well as the injectors. Try running it through at least three full tanks of gasoline before evaluating the results [source: Allen]. And have you seen those advertisements on gas pumps that promote gas manufacturers' brands of "cleaner engine" fuel? This is why -- detergent cleaning additives are required by the U.S. Environmental Protection Agency [source: Federal Trade Commission]. (All octane levels should perform similar cleaning functions.)
Next, check the spark plugs. It's a simple process, but if you're uncomfortable or don't have the right tools, it's best left to a mechanic. Once the plugs are out, compare the model numbers stamped onto the plugs with your manufacturer's recommendation (which can be found in your owner's manual). If the spark plugs were the right kind, well, it's a good thing you're probably already at your mechanic's, because your car's got other problems.
Keep reading for more information about filthy and finicky engines.