Why can't the car accelerate when driving at 120 km/h on the highway?
4 Answers
This situation is generally caused by the fuel system. It is necessary to check whether the fuel injector is clogged, which affects the fuel supply effect. Check the atomization effect, and use a fuel pressure gauge to measure whether the fuel pressure meets the standard. Generally, low fuel pressure, insufficient fuel pump supply in the system, damaged fuel pressure regulator, clogging, fuel filter issues, or overly lean air-fuel mixture can also lead to poor acceleration. Here is more related information: Precautions: At high speeds, the transmission will stay in a high gear, so the engine speed will not be too high. If the speed is 120 km/h, the engine speed will be around 2000 rpm. At this time, the engine will be in a low-speed, high-load condition. According to engine theory, low-speed, high-load is the most 'comfortable' working state for an internal combustion engine, with relatively high thermal efficiency, so there is no strong demand for cooling. On the contrary, if you frequently overtake in the city using low gears, the engine will often operate in a high-speed, low-load condition, with low thermal efficiency, which requires higher cooling performance.
When driving on the highway, if you frequently encounter the issue of not being able to accelerate beyond 120 km/h, it's mostly due to engine performance problems. The most common issue is old spark plugs failing to ignite, which causes the engine to lose power. Another possibility is a clogged fuel filter leading to insufficient fuel supply, resulting in sluggish acceleration. At high speeds, the engine is under heavy load, making these problems more apparent. When inspecting, first check if the spark plugs are burnt out—try replacing them with new ones. Also, examine the fuel filter for cleanliness; replace it immediately if it's clogged. Additionally, dirty fuel injectors causing poor spray patterns are also common and can affect acceleration performance. Regular maintenance is crucial—replacing spark plugs every 20,000 km and cleaning the filter periodically can significantly reduce such issues. Slow acceleration is especially dangerous on highways, particularly during emergency overtaking, which can easily lead to accidents. Don’t ignore these signs; address them promptly or visit a professional repair shop to ensure safety.
When experiencing difficulty in acceleration, the first thing that comes to mind is an issue with the intake system—the engine is starved of air when it needs it most at high speeds. The most common culprit is a dirty or clogged air filter, akin to trying to run while wearing a mask that restricts breathing, leading to reduced fuel efficiency and sluggish acceleration. Over time, if the air filter isn't replaced, dust accumulates, or if the filter mesh is torn allowing dirt to enter, these problems arise. A simple DIY check involves popping the hood, pulling out the air filter, and replacing it if it appears dark-colored. Ignoring this can cause fuel consumption to spike and accelerate engine wear; a muffled engine roar at high speeds is a telltale sign. Address this promptly to avoid overheating and potential breakdowns, which can shake driving confidence. Regular maintenance, including frequent air filter cleaning or replacement, ensures smooth and worry-free high-speed performance.
My car has transmission issues causing difficulty accelerating at high speeds, especially noticeable with automatic transmissions. Internal transmission slipping or failure to engage gears leads to poor power transfer, particularly evident around 120 km/h. I tried manually downshifting to observe the response—if pressing the accelerator deeply results in slow RPM increase accompanied by noise, it's likely a concern. Old, overly thick transmission fluid or low fluid levels can also cause faults, making fluid inspection crucial. Cloudy or dirty fluid indicates the need for replacement. Ignoring minor transmission problems can lead to major repairs. High-speed acceleration lag poses significant risks, so prompt troubleshooting is essential to avoid hazards.
