Engine Knocking – Pinging – Rattling Noise – Common Causes

Engine Knocking - Pinging - Rattling Noise - Common Causes
Engine Knocking - Pinging - Rattling Noise - Common Causes

Is your engine making an annoying knocking, pinging or rattling sound when you accelerate.

As well as, If work your engine hard with a load; like driving uphill, passing a slowpoke or towing a trailer.

Then, Most likely you’re probably experiencing spark knock. (engine knocking)

So, What do you think is making that engine knocking noise.

It’s not necessarily a problem with your fuel delivery system.  It does mean that your fuel is detonating, or exploding erratically rather than burning smoothly as it should.

Eventually, this could lead to a failed head gasket, broken rings, cracked piston lands and/or flatten your rod bearings.

Thankfully There Are Ways To Narrow The Engine Knocking Noise:

First Check If The (EGR) Valve Is Working

The (EGR) valve should open when ? The engine is accelerating or lugging under a load. This allows intake vacuum to suck some exhaust in through the (EGR) valve to dilute the air/fuel mixture slightly. This lowers combustion temperatures and prevents knock.

Automotive Engine (EGR) Valve
Automotive Engine (EGR) Valve

Inspect the operation of the (EGR) valve; and check for a buildup of carbon deposits on the valve pintle or valve port; that may be blocking the flow of exhaust back into the engine. Clean off the carbon deposits with a wire brush and carburetor cleaner; or replace the (EGR) valve if it is defective.


Next Check If The Engine Knock (KS) Sensor Is Working

Your engine has a knock (KS) sensor that should detect detonation and tell the computer to retard the ignition timing. If your engine requires premium grade fuel; but you are using regular or mid-grade fuel; the knock sensor should detect any detonation that may occur when; the engine is working hard under a load and cause the (PCM) to retard timing.

Knock Sensors (KS) Bolted To Engine Block
Knock Sensors (KS) Bolted To Engine Block

This reduces power a bit but protects your engine against detonation. However, if the knock sensor is not working, spark timing will not retard when it should. Consequently, you may hear a pinging or rattling sound (spark knock) when accelerating, driving up a hill; or when the engine is lugging under a heavy load.

Testing The Knock (KS) Sensor

The knock (KS) sensor can be tested by tapping on the engine near the sensor. You should do this while watching spark timing and/or knock (KS) sensor input; on a scan tool to see if it sends a timing retard signal.


NOTE: Over advanced ignition timing can also cause the same thing (engine spark knock). The only way to change the timing advance would be to flash reprogram the (PCM).


Excessive Carbon Buildup In The Combustion Chambers And On The Tops Of The Pistons

This is usually more of an issue with older engines. This includes vehicles that are only driven for short trips and never fully warm up. Treating the engine with a dose of top cleaner or a fuel system additive that also removes carbon from the combustion chamber; can usually clears this up.

Carbon Buildup On Piston
Carbon Buildup On Piston

Some repair shops use a machine to perform an engine carbon cleaning procedure. The machine uses a concentrated detergent to flush out the fuel injection system and combustion chambers.

Compression Ratio Too High

If the cylinder head has been resurfaced to restore flatness; this will reduce the volume of the combustion chamber and also increase the engine’s static compression ratio. These changes will increase engine power; but also the risk of detonation on regular 87 octane fuel.

Resurfaced Cylinder Head
Resurfaced Cylinder Head

Such modifications may require using higher octane 89 or 93 octane premium fuel and/or retarding spark timing. Engines that are supercharged or turbocharged are also at much higher risk of detonation; because the forced air induction system increases compression. This usually requires using premium fuel.

Using Low Quality Or Cheap Gas

Regular grade gasoline is supposed to have an octane rating of 87. If the gas station or their refiner is cutting corners and the fuel is not 87, it may knock. The fix for this is to try a tank of mid-range or premium gasoline.

Low Quality Or Cheap Gas
Low Quality Or Cheap Gas

Or, if you always buy gas at the same gas station, try a different gas station. Also don’t buy the cheapest gas you can find.

Engine Overheating

If the engine is running too hot because of low coolant, a cooling fan that isn’t working; a clogged radiator, bad water pump, sticking thermostat, etc., it may cause the fuel to detonate.

Automotive Engine Overheating
Automotive Engine Overheating

If you’ve got an overheating problem, and you’ve checked the radiator fan and radiator; plus replaced the thermostat, chances are you’ve got a failing water pump.

Conclusion

So, Spark knock (detonation) is an erratic form of combustion; that occurs when multiple flame fronts occur simultaneously inside a combustion chamber. Detonation occurs because fuel is subjected to either too much pressure, too much heat or both.

Abnormal Combustion Causing Engine Knocking
Abnormal Combustion Causing Engine Knocking

Instead of a single flame front growing outward smoothly like an expanding balloon from the point of ignition; multiple flame fronts are generated spontaneously throughout the combustion chamber; as the fuel automatically ignites from heat and pressure. Finally, The multiple flame fronts collide, creating shock waves that produce a sharp metallic pinging or knocking noise.

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