Let’s talk about engine knocks. Trojan Auto Care can get to the bottom of the reason why your car, truck, or C/SUV’s engine keeps knocking. In certain cases, it’s important to find the source of the knock and resolve it to prevent engine damage.
Loose Accessory Belt
Let’s start with something that can make it sound as if your engine is knocking when it really isn’t. A loose accessory belt will smack around inside the engine and make a knocking sound. This isn’t engine knock. The belt just needs to be tightened to resolve the problem.
Timing That Is Bad
Bad engine timing can cause the engine to knock. Basically, the knocking sound that you hear is the spark plugs misfiring. There are two reasons why the plugs will misfire. The first is that the plugs are worn and need to be replaced. The second is a malfunctioning engine control unit.
Bad Knock Sensor
You might also have a bad knock sensor in the engine and this is why the engine is knocking. The knock sensor sends an error code to the engine control unit if the engine is knocking. This allows the unit to make changes in the combustion chamber to, hopefully, stop the knocking sounds.
Air-Rich Fuel Mixture
One of these changes is adding fuel to a lean fuel mixture to balance it out. A lean mixture is heavy in air and fires multiple times rather than just once. These multiple firings in the cylinders are the knocking sound that you hear. A clogged fuel filter or faulty fuel pump can cause a lean mixture.
Low-Octane Gasoline
Another thing that will make your engine knock is gasoline that has a lower octane rating than what your engine needs. In other words, don’t put 87 in the tank if the owner’s manual says your engine needs 89 or 91. The lower octane will fire multiple times in the cylinders.
Bearings That Are Worn
Finally, we mentioned above that, sometimes, a knocking engine can become a damaged engine. This is the case if the cause of the engine knock is worn rod bearings. Unfortunately, in this case, the knocking sound that you hear is the pistons crashing against the cylinder walls as they go up and down.
You don’t need us here at Trojan Auto Care in Troy, OH, to tell you that this can damage the cylinder block beyond repair. As such, stop by our shop as soon as possible if your engine is knocking.
