If your car, truck, or C/SUV’s engine is knocking, there could be a detonation, bearing, or belt problem. BJ’s Automotive is going to list the common causes of a knocking engine below. It’s important to have the issue resolved as soon as possible, as some of the causes that we are going to list can actually damage the engine. You don’t want your engine to knock. It should run smoothly.
A Malfunctioning Knock Sensor
Your vehicle’s manufacturer does not want your engine to knock, either, which is why it installed a knock sensor in the engine. This sensor alerts the engine control unit when the engine is knocking to give the unit a chance to make adjustments in the combustion chamber to stop the knocks. If the knocks sensor is malfunctioning, it may not notify the engine control unit that the engine is knocking.
An Air-Heavy Air/Fuel Mixture
One thing that the engine control unit can do if the engine is knocking is to add fuel to the combustion chamber to resolve the problem of an air-heavy fuel mixture. This is a lean fuel mixture and it will make your engine knock because there is not enough fuel in the mix to generate just one detonation per cylinder. The excess air causes multiple detonations – the knocking sound – in the cylinders.
Spark Plugs That Are Misfiring
Another thing that can cause multiple detonations is spark plugs that are misfiring. The plugs may be misfiring because they are old and worn. Replacing the old spark plugs with new ones will stop the engine from knocking. The spark plugs may also be misfiring if the engine control unit is having problems and firing the spark plugs multiple times or out of order.
The Wrong Fuel Octane Rating
You may also end up with a detonation knock if you put the wrong octane rating in the tank. In this case, let’s assume for the moment that you drive a high-performance vehicle, or maybe you do. This engine requires fuel with an octane rating of 91 or 89 at a minimum. Putting 87 in the tank will make the engine knock because the fuel will fire multiple times.
Rod Bearings That Have Worn Out
As we mentioned in the introduction to this article, bearings can also make the engine knock. In this case, the bearings are the rod bearings and they help the rods move up and down inside the cylinders. The rods actually push the pistons up and down in the cylinders. If the bearings are worn, the rods will slam the pistons against the cylinder walls. This is the noise you hear.
Finally, BJ’s Automotive in Everett, WA, advises that a loose accessory belt can also make a knocking sound in the engine as it slaps against other engine parts. Call us today if your engine is knocking.