Rough Idle in Cars: Causes and Solutions
Rough Idle in Cars: Causes and Solutions

Rough Idle in Cars: Causes and Solutions

10/02/2025
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A friend in Long Bien, Hanoi, recently bought a Hyundai HD120s truck and experienced rough idling after a while. Worried about bad luck, he consulted a fortune teller who blamed it on evil spirits. Fortunately, he also took the truck to Thai Phong Auto Repair on Nguyen Van Linh Street. The technicians diagnosed and fixed the problem – it wasn’t supernatural, just some faulty parts.

What is Rough Idle in a Car?

Rough idle, also known as engine surging, is when a car’s engine runs unevenly, causing jerking or hesitation when accelerating. The engine may stall when accelerating quickly or going uphill. This is not only annoying but also dangerous, especially at high speeds or in heavy traffic.

Causes of Rough Idle in Cars

Several issues can cause rough idle. Here are some common culprits:

1. Clogged Fuel Filter

The fuel filter removes dirt and debris from the fuel before it reaches the engine. A clogged filter restricts fuel flow, leading to rough idling and engine surging.

2. Weak Fuel Pump

The fuel pump delivers fuel from the tank to the engine. A weak pump provides inconsistent fuel flow, causing the car to jerk when accelerating.

3. Faulty Throttle Position Sensor

The throttle position sensor tells the engine control unit (ECU) how much air to let into the engine. A faulty sensor prevents the ECU from accurately adjusting airflow, resulting in rough idle.

4. Worn Spark Plugs

Spark plugs ignite the fuel-air mixture in the engine cylinders. Worn, weak, or faulty spark plugs produce a weak spark, leading to incomplete combustion and rough idling.

5. Stuck EGR Valve

The Exhaust Gas Recirculation (EGR) valve recirculates some exhaust gas back into the combustion chamber to reduce NOx emissions. A stuck EGR valve disrupts airflow, causing rough idle.

Stuck EGR ValveStuck EGR Valve

Estimated Cost to Fix Rough Idle

Issue Estimated Cost (VNĐ)
Fuel filter cleaning/replacement 500,000 – 1,000,000
Fuel pump inspection/replacement 1,500,000 – 3,000,000
Throttle position sensor cleaning/replacement 500,000 – 1,500,000
Spark plug replacement 500,000 – 1,000,000
EGR valve cleaning/replacement 1,000,000 – 2,500,000

Note: These prices are estimates and may vary depending on the car model, make, and repair shop.

What to Do if Your Car Has Rough Idle

  • Take your car to a reputable auto repair shop for diagnosis and repair as soon as you notice rough idle.
  • Avoid attempting DIY repairs without proper knowledge and tools, as this could worsen the problem.
  • Choose a reputable auto repair shop with modern equipment and experienced technicians for safe and effective repairs.

Reputable auto repair shopReputable auto repair shop

Frequently Asked Questions

Q: Is rough idle dangerous?

A: Yes, rough idle can be dangerous, especially at high speeds or in heavy traffic. It can cause jerking, making it difficult to control speed and increasing the risk of accidents.

Q: What should I do if my car has rough idle?

A: Take your car to a reputable auto repair shop for diagnosis and repair immediately.

Q: How much does it cost to fix rough idle?

A: The cost depends on the cause and severity of the problem.

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Similar Products

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  • Hyundai
  • Isuzu
  • Hino
  • Thaco Trường Hải

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