There are two things that can make your car, truck, or utility vehicle’s engine knock all the time. The more common of the two is detonation knock. Your engine might also be knocking because of rod knock. Willoughby Hills Auto Repair is going to discuss the two below in greater detail and what causes each. A knocking engine can be a damaged engine, so bring your vehicle to our shop right away if your engine is knocking constantly. We will find the cause of the knock and fix it.
Detonation Knock
In an efficient engine, air and fuel is mixed in the combustion chamber and put in each cylinder to be ignited by the spark plugs. This creates a tiny fireball in each cylinder that generates engine combustion. Detonation knock occurs when there are multiple fireballs in each cylinder. In other words, instead of having just one firing in each cylinder, there will be multiple firings. These tiny explosions are the knocking sound that you hear coming from your engine if it has a detonation problem.
Your car’s engine has a sensor that listens for knocking sounds. Once it hears knocking, it notifies the main computer chip, the engine control module. This gives the engine control module a chance to assess the situation in the combustion chamber and make necessary adjustments to prevent multiple detonations in each cylinder. If the knock sensor has gone bad, this is one reason why your engine could be knocking. Other reasons include
- A lean fuel mixture in the chamber that is rich with air
- A problem with the engine timing that causes the spark plugs to misfire
- Gasoline in the tank that has octane that is too low for your engine
The latter is one of the most common reasons why an engine knocks. You may think that your engine will do fine with gasoline that has an 87-octane rating, but if your engine needs 91 or 89, it will knock while it burns the fuel with the lower octane.
Rod Knock
Rod knock happens when the rod bearings wear out. The pistons rely on rods to move them up and down inside the cylinders without making contact with the cylinder walls. Worn rod bearings cause the rods and pistons to shift and bang against the cylinder walls as they move up and down. Unfortunately, this causes rod knock. Failure to repair this issue can cause serious damage to your cylinder block.
Willoughby Hills Auto Repair in Willoughby Hills, OH, is here to help, so call us today if you are having a problem with a knocking engine.