Have you become aware of a strange engine noise on your car recently? It seems to be a rhythmic, tapping sensation which becomes more noticeable when you accelerate. This is known in the industry as "knocking" and is something that you need to fix as soon as possible. What can cause this and what should you do in order to rectify it?

Figuring It out

Typically, this issue is caused when the mixture that enters the combustion chamber is incorrect. You may have to go through a process of elimination to find out what's causing this, as it could be traced to a number of different components.

Use the Proper Fuel

For example, you could check to see if you have been putting the right grade of petrol into the tank recently. Some people think that they can save some money by going down one grade, but the engine is designed to take a particular type of fuel. You may also find that a bottle of octane booster would help, as you go back to the right grade.

Clean the Chamber

Sometimes, a bad batch of fuel will have introduced some unwanted additives to the system. When contaminants get in to the engine they can sometimes leave a residue within the combustion chamber which can contribute to these noises. Go to your auto-parts store and buy a bottle of fuel detergent and add this to your next tankful of petrol.

Check the Timing

Sometimes, the timing of the engine itself will "slip" and while this is an unusual occurrence, it needs to be put back to its original specification. There is actually a special mark engraved on the rear of the engine, near to the transmission's bell housing. You will need a timing light (which you can get from your parts retailer) and you'll need to connect this to the primary spark plug. Refer to your owner's manual for the correct readings as you aim the timing light at the mark on the bell housing.

Change the Spark Plugs

You may also find that it's time to change the spark plugs, especially if you haven't done so in some time. It's possible to adjust the "gap" using a special gauge if you simply want to work with the plugs that you have right now, but these are relatively inexpensive parts and have a big job to do. As a consequence, it's best if you replace them instead.

Getting Replacements

Ask your auto parts expert to provide you with these parts and give you some additional advice, if you're still not sure.