Causes of engine knock
FAULTY SPARK PLUGS
Your engine’s spark plugs deliver the electric spark that ignites the cylinder’s fuel/air mixture. In other words, spark plugs are essential to getting your engine up and running! Like other parts in your car, spark plugs age and break down over time. Most auto manufacturers recommend having new spark plugs installed about every 30,000 miles, but spark plug longevity depends on the condition and type of spark plug. If you’re not using a manufacturer recommended spark plug, or your spark plugs have seen better days, this could be what’s causing that distracting knock
DIRTY CYLINDER WALL
These may be carbon deposits. When deposits form, the volume of the cylinder is effectively decreased. As a result there occurs an increase in compression that can cause a car to knock. To combat this, first try to purchase some detergent additive at an auto parts store, and then try switching fuels. If your car is prone to knock, you may want to add the detergent at every fill-up.
BAD SPARK PLUGS
Using the wrong spark plugs can also cause knocking in your engine as an incorrect fit can impede performance. Engines are precise machines, meaning you can’t swap out your spark plug for an aftermarket option that almost fits because the performance will likely suffer.
LOW OCTANE FUEL
Gasoline comes with different octane ratings, which is why you have so many options when you pull up to the pump. The higher a fuel’s octane rating, the more compression it can withstand before igniting. If your engine was engineered to handle high-octane fuel, using the regular kind could lead to excess engine noise. High-octane fuel does tend to be more expensive than regular fuel. While saving a few bucks at the pump may seem like a great reason to go with regular, engine knocking means it may be time to spend a little more. Long-term use of the wrong fuel could damage your engine and decrease your fuel economy.