Why does my Yaris (2020 new look) slows down when accelerating hard?

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Why does my Yaris (2020 new look) slows down when accelerating hard?

Last updated
Relly De Jesus
Toyota Mechanic

Hello and welcome to ExpertHelp.com! My name is Relly De Jesus and I'm going to do everything in my power to answer your question to your full satisfaction!

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Last updated
Relly De Jesus
Toyota Mechanic

Hello Duvnjak

Hope everything is well. There are few things to look at to resolve this issue and below is a list. It's a long one but worth to read to resolve the problem.

1. Air intake filter - the air intake filter can be dirty or clogged that it can restrict the airflow to the engine which can make it sluggish on sudden or hard accelerations.

2. MAF sensor - The mass air flow (MAF) sensor, part of your vehicle's electronic fuel injection system, is responsible for calculating the total amount of air entering the engine. A contaminated or failed mass air flow sensor cannot measure the amount of air flow correctly.

3. Fuel Filter -  If the fuel filter is clogged in your Toyota Yaris, not enough fuel can get into the engine. This causes loss of power and jerking of the vehicle when accelerating. In worse case scenario, engine cuts out while driving due to insufficient fuel supply.

4. Catalytic Converter - common signs of clogged catalytic converter in Yaris are irregular running of the engine, unusual exhaust gas odor, poor fuel economy, engine check light illuminates, limited performance above a certain speed or loss of performance, and sometimes rattling noises.

5. Oxygen Sensor - Faulty oxygen sensors are the leading cause of catalytic converter failures. If you suspect a problem with O2 sensor, you should act immediately and get it checked by a professional mechanic. O2 sensors are relatively cheap compared to the price of catalytic converters, which can easily cost you over a thousand dollars to replace.

6. Throttle body - One of the main causes of a faulty throttle is internal contamination. The throttle valve regulates the supply of air to the internal combustion engine. Over time, dirt and grime that escapes through the air filter can accumulate in the throttle body, this results in improper throttle valve movement, which causes problems with the control of the air supply.

7. Throttle Position Sensor - The throttle position sensor or TPS is used to determine the opening angle of the throttle valve. The information obtained is sent to the control unit and contributes to the calculation of the amount of fuel required. The symptoms of defective throttle position sensor in Yaris are usually reduced engine performance, engine jerks, RPM fluctuations when idling and a slow drop in speed after the driver has released the accelerator.

8. Fuel Pump - The fuel pump in your Toyota Yaris is like a beating heart that pumps fuel to the engine when the vehicle is running. A malfunctioning fuel pump can result in irregular or decreased acceleration, poor engine starting behavior, engine jerking or stalling while driving and a decrease in fuel efficiency.

9. Spark plugs and Ignition coils - 

If the spark plugs in your Yaris are not generating sparks properly, the engine will no longer run optimally. This is often noticeable in a loss of performance and increased fuel consumption. You may also notice that the engine is not running smoothly or the engine is jerking while driving – sometimes the engine simply cuts out. If you continue to drive with a defective spark plug, you run the risk of very expensive consequential damage, for example catalytic converter failure.

The ignition coils are part of the ignition system on your Yaris and are responsible for amplifying the relatively low battery voltage from 12V to a high voltage of tens of thousands of volts for the spark plugs. A fault in an ignition coil can cause poor sparking which can result in poor engine performance. The symptoms of a bad ignition coil are more or less the same as a bad spark plug.

10. Fuel Injectors - 

Fuel injectors are part of the fuel delivery system that sprays fuel in the form of a high-pressure mist. Over time they can get clogged due to hydrocarbons, sediment and other elements in the fuel. When that happens, proper amount of fuel can no longer be delivered to the combustion chamber at the correct pressure.

Common symptoms of clogged fuel injectors in Toyota Yaris are slow acceleration, rough idling, irregular engine performance, increased fuel consumption, engine hesitation and misfiring.

11. Engine oil filter - The engine oil filter in your Toyota Yaris ensure that the engine oil remains free of dirt particles, metal shavings, soot or unburned fuel, thus preventing damage. If the filter becomes clogged, it can cause the engine to sputter, the faster you drive, the more it sputters.

12. Transmission - 

A malfunction in the transmission can also be responsible for slow acceleration problem in your Yaris. Transmission is a complex component, it is responsible for transferring the power from the engine to the wheels. There are many gears that mesh with one another. Sooner or later this friction leads to wear on the components, especially if your Yaris has racked up a lot of miles or if you didn’t change transmission fluid in time.

A faulty transmission usually show other signs including grinding or clunking noises, jerky acceleration and burning smell.

It can be a worn out piston rings, valve seals or a blown head gasket but since it's a 2020 you can start with the ones listed above first. You can take it in to a reputable shop or mechanic for a physical diagnostic as well and I'm pretty sure that he can check everything and find what's causing this issue.

Hope this helps and please let me know if there's anything else I can help you with. You have a good one!





Thanks for youranswer.

The thing it that it only did it twice yesterday and hasn't done it before or since. I've only had the car for 24 hours. Do you think it could be some safety feature stopping the car going too fast after it reads a road sign speed limit sign? 

Relly De Jesus
Toyota Mechanic

Hello Duvnjak

Good to hear back from you. If the car is equipped with such safety features then it could be the cause. Since its only a 2 year old car I don't see any reason for the given parts to fail. Mostly it will show up after 5 years or more. Since it's a  Toyota it's a dependable car and can withstand any driving habits. But it's best to have it checked physically by a reputable mechanic/shop to have a peace of mind though. But if the issue seems to be tolerable, I don't see any problem.

Anything I can help you with Duvnjak? I'll be standing by for your response

Thank you




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