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How Mechanic Training Can Help You Diagnose and Fix “Engine Knock”

Published on March 1, 2018 by in Blog, CATI

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As a car mechanic, you will probably experience a fair share of clients coming in worried about a mysterious noise under their hood. Quite often, you will likely be able to diagnose this problem as ‘engine knock’, also known as pinging or detonation.

Engine knock signifies that something is off with an engine’s spark ignition system. Not addressing the issue promptly could result in quite serious engine component damage, so a speedy and correct diagnosis by a trusty mechanic is a car owner’s best bet to averting more serious problems. To find out how mechanic training can help prepare you for addressing engine knock, keep reading!

Pros With Mechanic Training Know Engine Knock is Caused by a Disruption in a Car Engine’s Cycle

Automotive school grads know that a car’s engine works according to its own regular cycle, whereby a piston compresses a fuel and air mixture to a certain pressure at which it’s ignited by the engine’s spark plug. The proper functioning of this cycle depends on there being a favorable environment in the compression cylinder.

When something disrupts this environment, it changes the balance between pressure and heat in the compression cylinder which throws off the engine’s cycle. The resulting irregular cycle forms high pressure waves which end up making engine knock’s signature pinging noise. Typically, the disruption is caused either by the use of the wrong fuel, carbon deposits in the engine, or a spark plug problem.

Simply Using Fuel With the Wrong Octane Rating Can Lead to Engine Knock

Have you ever wondered why you can choose from various types of fuels at the gas pump? The reason is that different engines are designed for different fuels with varying octane ratings. The higher a fuel’s octane rating, the longer it will take to ignite, waiting for the precise moment in the piston’s stroke to be ignited by the spark plug. If a car is running on fuel with an octane rating lower than that recommended by the manufacturer, the fuel will ignite on its own earlier than the spark plug lights it, which can lead to engine knock.

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Cars should run on the correct fuel to prevent engine knock

Fixing this problem usually just takes adding an octane booster to the existing fuel, or switching out for the proper fuel. However, professionals with mechanic training should make a careful assessment of whether the use of improper fuel significantly altered an engine’s compression ratios, which might warrant their adjustment before the engine knock can be completely fixed.

Carbon Buildup is Often the Culprit Behind a Pinging Engine

Over time, and also as a result of using the wrong fuel, carbon debris that forms when fuel is burned can stick to various engine components. If these build up, they can significantly alter the volume within a compression chamber and disrupt compression ratios, causing engine knock.

Fortunately, this issue can usually be solved by adding a cleaning additive into the gasoline. This should actually be done regularly to avoid carbon buildup, because even one errant carbon ember in the combustion chamber can ignite separately from the primary flame front and disrupt the engine’s cycle.

Spark Plug Issues Could Also Be Causing Engine Knock

Just like each engine should use the gasoline which is recommended for it, manufacturer’s guidelines should also be adhered to when it comes to the spark plug. Any issues with the spark plug can again disrupt the entire delicate combustion system.

Not only does the spark plug have to be the correct one for the particular car, it also needs to be set up just right to ensure that the firing temperature and timing are perfect. Engine knock in relation to a spark plug problem can be corrected either by replacing the spark plug or correcting any ignition timing issues it may have.

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Improper spark plug settings could be the culprit behind engine knock

Though these are the three most common problems that can cause engine knock, there are still a host of other issues which may be the culprit. Diagnosing the problem correctly can be tricky, so it’s best to advise your clients to always see a qualified mechanic in the event of engine knock.

Are you wondering how to become an auto mechanic in Ontario?

Explore the program offered by CATI!

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