Knock Sensors: What They Are, How They Work, and Their Role in Preventing Engine Knock
The engine is the automotive equivalent of the human heart, so it is critical to keep it working and in good condition. But what does it mean when it starts making strange noises?
Struggling engines can make a range of different noises. Each can mean a different thing.
A whirring or whining noise from the engine can indicate low fluid levels (in particular power steering fluid), or a malfunctioning alternator/alternator bearing. A squealing noise from your engine can be quite alarming, and is most likely caused by the serpentine belt wearing out and slipping. If you hear a grinding noise from under the bonnet, this is usually to do with worn-out bearings.
If you hear a (non-metallic) tapping or knocking sound from the engine, this could simply mean that your oil level is low (and needs replenishing). If you hear a metallic ticking, pinging, or knocking sound, this can mean an issue with the cylinders and how they are dealing with the fuel and air mixture inside them.
What is engine knock?
Engine knock is a distinctive metallic knocking, pinging, or ticking sound that occurs when there are issues with one of the engine's cylinders. It usually means that the fuel and air mixture within the tank is detonating in multiple places at the same time. Also known as detonating knock, this issue can cause damage if not addressed promptly.
What is a knock sensor?
A knock engine sensor is a specially-designed listening device that is usually attached to the exterior of the engine block.
What does a knock sensor do?
A knock sensor detects irregular vibrations or strange sounds such as knocks. If it detects a knock, it will relay this information to the ECU which then decides what to do. It may alter the ignition timing, illuminate the Check Engine Light (CEL), or even shut down part of the engine.
How does a knock sensor work?
Most knock sensors use 'smart' materials that are able to convert mechanical effects (pressure, vibration, noise) into electric signals.
Engine maintenance
There are a number of things you can do to ensure your engine stays healthy and lasts longer.
The most useful ones are: change your oil and oil filter regularly (around every 5000 miles), regularly top-up your coolant, replace your air and fuel filters regularly, check for leaks, check your belts, pay attention to any warning lights, try to keep your speed and RPM at a consistent level when driving, and get your spark plugs and leads changed around every 30,000 miles.
Protyre - the tyre specialists
Protyre is also one of the largest online tyre retailers in the UK, with a network of over 180 garages offering tyre fitting, servicing and free checks. Some even offer same-day appointments. Protyre garages stock a range of tyres to suit all needs. This includes premium tyres from leading brands such as Goodyear, Michelin, Pirelli, and Bridgestone; mid-range tyres from the likes of Sumitomo, GT Radial, and Falken; and low-cost options from brands including Ovation, Budget, and Autogrip.
The available selection incorporates summer, winter, and all-season tyres as well as XL and UHP tyres.
Protyre safety checks - brakes and more
Did you know that Protyre garages offer a range of free safety checks for your car? As well as brakes, these include checks on suspension, alignment, battery, tyres, exhaust, TPMS, steering, and aircon. Additionally, we offer a free 6-Point seasonal safety check.
Protyre - additional offerings
As well as tyre-fitting and safety checks, Protyre garages also offer MOTs and servicing.
Frequently Asked Questions
Engine knock (also called detonating knock) is a distinctive metallic noise that comes from the engine. It is caused by multiple simultaneous detonations occurring within a cylinder.
The leading causes of engine failure include overheating, lack of maintenance, lack of lubrication, fatigue, incorrect oil/fuel, inadequate filters, and detonation/pre-ignition.
There are actually quite a lot of different engine types. Most are variants of internal combustion engines with different fuel types, numbers of cylinders and different layouts. More recently, hybrid and electric motor engines have been developed specifically to meet demand for greener cars.
As a general rule, traditional diesel or petrol combustion will last for 18-20 years or around 200,000 miles. However, this can be extended with proper car maintenance. These figures are projected to be similar for both hybrid and fully electric vehicles although battery-based EVs will require battery replacement at around 8 years or 100,000 miles.