A knocking noise in the engine of your 2020 Toyota RAV4 can be indicative of several potential issues. It's important to address this promptly to avoid further damage to your vehicle. Below are some reasons why this might be happening, along with potential solutions:

 
Low-Quality Fuel
 

•   The quality of fuel being used can significantly affect engine performance. Low-octane fuel may lead to knocking noises.
•   Check your vehicle’s manual to confirm the recommended octane rating for your RAV4, and ensure you're using the correct gasoline.

 
Engine Timing Issues
 

•   Incorrect engine timing can cause the valves to open or close at improper intervals, leading to a knocking sound.
•   Have a qualified mechanic inspect the engine’s timing belt or chain to ensure it's properly aligned and functioning.

 
Detonation or Pre-Ignition
 

•   Detonation, otherwise known as engine knock, occurs when fuel ignites prematurely in the combustion chamber. This can result in a knocking noise.
•   Ensure that the air-fuel mixture is correct and have the engine control unit (ECU) checked for potential software updates or malfunctions.

 
Carbon Build-Up
 

•   Excessive carbon deposits inside the combustion chamber can increase compression ratios and lead to knocking sounds.
•   Consider a professional cleaning of the engine’s internals to remove carbon build-up.

 
Worn Engine Bearings
 

•   The bearings that support the engine’s moving parts can become worn over time, causing knocking sounds as the parts move.
•   This is a more serious issue that usually requires the attention of a professional mechanic to replace the worn bearings.

 
Faulty Knock Sensor
 

•   The knock sensor is responsible for detecting engine knock and adjusting engine timing to prevent it. If faulty, it may not correctly adjust the engine timing.
•   A malfunctioning sensor should be diagnosed by a professional and replaced if necessary.

 
Low Oil Pressure
 

•   Low oil pressure can cause inadequate lubrication of engine components, leading to increased friction and a knocking noise.
•   Check the oil level and pressure, and consider changing the oil if it hasn’t been maintained recently.

If you suspect any of these issues or feel uncomfortable diagnosing the problem yourself, it’s advisable to consult a professional mechanic for a comprehensive inspection.