Noises
Knocking or pinking from the engine: what it means and what to do
A metallic knock that rises with engine speed from deep inside the engine can mean worn bearings or a lack of lubrication, and it is very serious. A light rattle when accelerating under load is usually pinking, and a ticking from the top of the engine, the hydraulic lifters.
Stop as soon as it is safeNoises
Reviewed by Daniel Morales, founder of Reprorace SL, on
Is it serious? Can I keep driving?
Do not keep driving. If the knock is deep, rises with the revs or comes with the oil light, stop as soon as it is safe and switch off the engine: carrying on can destroy it. If it is light pinking when accelerating, have it checked soon and avoid loading the engine.
A careful, general answer: only someone who inspects the car can say whether it is safe to drive. When in doubt, stop somewhere safe and call for assistance.
Most likely causes
- Pinking (detonation): fuel with a lower octane rating than specified, carbon deposits or a knock sensor that does not correct.
- Lack of oil or pressure: parts knock without lubrication; ticking hydraulic lifters are an early warning.
- Worn big-end or main bearings: a dull knock that grows with engine speed and load.
- Timing drive: a stretched chain or a tensioner that does not tension gives a metallic noise on start-up.
- External parts: a loose heat shield or exhaust bracket can sound similar.
Listed from more to less common in general; on your car they may be different. A fault-code reading and a check at the garage confirm which one it is.
To understand it better: What are engine misfires (P0300)? What do the crankshaft and camshaft sensors do and what happens when they fail?
Car system: Engine and lubrication
What you can check yourself
Check the oil level on level ground with the engine cold.
Note whether the noise appears when cold, when accelerating under load or all the time, and whether it rises with the revs.
Make sure you use the fuel shown on the fuel flap or in the handbook.
With the car parked, look for loose exhaust parts or heat shields that rattle, without touching anything hot.
Safe checks only: with the engine off and cold whenever you look under the hood, without taking anything apart and without touching hot or moving parts.
Related fault codes
- P0325Knock/combustion vibration sensor A, circuit: malfunction
- P0327Knock/combustion vibration sensor A, circuit: signal low
- P0328Knock/combustion vibration sensor A, circuit: signal high
- P0332Knock/combustion vibration sensor B, circuit: signal low
- P0520Engine oil pressure sensor/switch A, circuit: malfunction
- P0011A camshaft position: timing over-advanced or system performance (bank 1)
Generic codes that often come with this symptom. Seeing one does not confirm the cause: it is where the diagnosis starts.
How the ECO-LITE helps diagnose it
Plugged into the OBD socket, the ECO-LITE reads the fault codes of the control units that answer, with the freeze-frame data captured when the fault happened, and shows live data on your phone or computer. With your permission, your garage can see them remotely before you bring the car in.
What to look at here: knock sensor signal and corrections if the car reports them, ignition timing, engine temperature and oil pressure where available.
Frequently asked questions
How do I tell pinking from a big-end knock?
Pinking is a sharp rattle when accelerating under load and usually stops when you lift off. A big-end knock is duller, rhythmic, rises with the revs and is heard without load too.
Does higher-octane gasoline fix it?
If the manufacturer asks for more octane than you use, it helps. If you already use the specified fuel, the problem is elsewhere.
Is ticking on a cold start serious?
If it lasts a few seconds and stops, it is usually the lifters filling with oil. If it persists or gets worse, check the oil level and condition.
Keep reading
- Engine and lubrication: how they work and what fails
- Oil warning light on: what it means and what to do
- Car jerks when accelerating: causes and what to do
- Car using oil: when it is normal and what to do
- Car symptoms: what they mean and what to do
- Check engine light on: what to do
- How to read and clear your car's fault codes
- OBD fault codes: what each one means