Things that Cause Knocking Noise from Vehicle When Accelerating - Service Information at Capitol Chevrolet

There are many instances where hearing a knocking sound can be a pleasant experience, like if a friend is stopping by for a visit. But a knocking that comes from your vehicle's engine is another story altogether. While there are different levels of severity, one thing remains constant: it's a problem that will need to be addressed by a pro right away. On this page, we'll take you through four of the most common reasons you might hear a knock from your engine. But, no matter what the cause, we strongly recommend that you have your vehicle inspected.

Dual-cam valvetrain

4. Valvetrain Trouble

The combustion chambers in your engine have multiple valves. To let the fuel and air mixture in, intake valves open up. Once combustion has happened, exhaust valves open to let the exhaust gases out. These valves are part of the valvetrain, and they are designed to open and close quickly and smoothly. A valvetrain that's not working as it should might cause a knocking, ticking, or tapping noise. This can be caused by excessive clearance between the components or by hydraulic valve lifters that are in disrepair,

Pistons in cylinders

3. Crankshaft/Rod Knock

The pistons that move up and down inside the cylinders are connected to rods, which are then connected to the crankshaft. Rod bearings maintain the proper amount of clearance between the connecting rods and the crankshaft--just enough to let oil pass through to keep the metal components from grinding against each other. However, this clearance can be increased if it's been too long since you've had an oil change, or if your oil levels are low. If the clearance gets too great, you may hear a knocking noise. This is caused by metal striking metal, and it probably means that your engine has been massively damaged.

2. Pre-Ignition/Detonation Knock

In gasoline engines, a perfectly-timed spark ignites a fuel and air mixture that's introduced into the combustion chamber in order to create combustion. However, it's possible for gas to combust from high compression before the spark has a chance to light. The result is a knocking or pinging sound. Though there are several potential causes of this, from an incorrect air/fuel ratio to timing that's a bit off, the most common cause of this kind of engine knock is using the wrong kind of fuel. The good news is that most Chevy models only require regular fuel. However, there are a few that need premium fuel, and inadvertently filling these vehicles with regular gas can cause this kind of engine knock.

Gas pumps showing different grades

1. Bad Knock Sensor

Ironically, engine knock can be caused by a knock sensor, which is designed to help combat knock! If the knock sensor detects engine knock, it can tell the car's computer to adjust the timing or the fuel/air ratio to stop the knock. A malfunctioning sensor can tell the engine to make incorrect adjustments that end up causing engine knock.



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