What causes the loud engine noise when stepping on the accelerator in a Vios?

[MacLucia]

The reasons for loud engine noise when stepping on the accelerator in a Vios are as follows: Excessive carbon deposits: Excessive carbon deposits in the engine is a major cause, primarily due to the use of inappropriate fuel. The solution is to recommend adding a certain amount of cleaner when refueling. After cleaning, it's best to drive at high speed for a while, which helps increase exhaust volume and allows stronger airflow to carry out larger carbon deposit particles. Damaged oxygen sensor: The oxygen sensor mainly monitors the fuel-air ratio in the engine. Once damaged, it can cause an imbalance in the engine's fuel-air ratio, leading to a sudden increase in fuel consumption. The solution is to check the oxygen sensor as an internal control unit of the car, and it should be replaced if faulty.

[StClayton]

I've been driving a Vios for ten years, and in this case, it's most likely an exhaust system leak. Aging exhaust pipe gaskets can cause a puffing sound, especially noticeable during rapid acceleration. Last time my car had this issue, it was because the front section of the exhaust pipe was cracked by a stone. Additionally, aging engine mount rubber pads can amplify vibration noise, particularly when accelerating in second gear, causing the dashboard to shake. A clogged air filter leading to insufficient air intake will cause the ECU to compensate by injecting more fuel, resulting in the engine roaring without much power and being noisy. I recommend first checking the exhaust pipe connections for black carbon deposits, then squeezing the engine mount rubber blocks to see if they're cracked. Remember to check when the engine is warm, as the leaking sound isn't obvious when the engine is cold.

[NatalieRose]

I pay special attention to maintenance and found the Vios throttle noise was loud, so I checked the oil condition first. I forgot to change the oil during the last service, and after driving 8,000 kilometers, I heard a clanking metal friction sound during acceleration. The belt system also frequently has issues: if the power steering pump belt is too loose, it will emit a screeching sound; if the tensioner pulley bearing is damaged, it produces a humming noise. Pay attention to the characteristics of the sounds: a metal knocking sound could be engine knocking, requiring carbon deposit cleaning; a rustling noise is mostly from the generator bearing. I open the engine compartment every month to listen for abnormalities, using a screwdriver to pinpoint the source of unusual noises by pressing it against components. Remember to change the oil every 5,000 kilometers, and the belts must be replaced every 60,000 kilometers.

[StCaleb]

From a professional perspective, it can be divided into three parts: intake, combustion, and transmission. For the intake system, check if the air filter housing clips are broken—80% of the Vios models I've repaired had air leaks and whistling due to this issue. For combustion problems, examine the electrode wear on the spark plugs; excessive gap can cause delayed ignition, resulting in knocking sounds. The most troublesome issue is clutch slippage, especially in manual transmission cars. If you press the accelerator deeply and the RPM surges but the speed doesn't increase, accompanied by a burning smell, it's likely the clutch. I often ask owners to start in third gear for testing—if the tachometer fluctuates noticeably, the clutch is done. It's recommended to focus on these three areas, and bringing an OBD scanner to check the air-fuel ratio data will provide more accurate diagnostics.