What are the reasons for high idle speed in winter that does not decrease even after the car warms up?

[LenaDella]

Winter car idle speed high does not decrease even after the car warms up reasons are: 1. Oil accumulation in the throttle and excessive carbon deposits on the throttle; 2. Weak spark due to spark plug failure; 3. Fuel line blockage, intake pipe failure; 4. Sensor failure causing the ECU to lose control; 5. Fuse blown, ignition module failure; 6. Low fuel quality. The methods to address high engine idle speed are: 1. Clean or replace the idle control valve and use a dedicated decoder for basic idle speed setting; 2. Locate the leak, reseal or replace related components; 3. Adjust or replace the throttle position sensor; 4. Clean and inspect the fuel injection volume of each injector to ensure no blockage or leakage; 5. Remove carbon deposits on the EGR valve or replace the EGR valve.

[Lindsay]

High idle speed in winter driving is common, but if it persists after the engine warms up, it's a cause for concern. Having driven for over a decade, I've encountered this issue several times and found it's often due to a thick layer of sludge buildup on the throttle body jamming the valve, especially as low temperatures harden these deposits making them harder to dislodge. Alternatively, it could be a faulty coolant temperature sensor causing the ECU to mistakenly think the engine is still cold and maintain higher idle speed. Once, I even resolved it by simply cleaning the sensor connector. Left unaddressed, not only does fuel consumption increase, but prolonged high idle can also wear down engine components. I recommend a thorough cleaning and inspection before cold weather sets in; doing it yourself with basic tools can save unnecessary repair shop expenses. Proper winter maintenance prevents many headaches, particularly for older vehicles that need extra attention.

[DelAliyah]

The idle speed control relies on the cooperation between the engine computer and various sensors. The high idle speed during cold starts is designed this way to accelerate engine warm-up. However, if it doesn’t drop after warming up, a common cause is a faulty temperature sensor sending incorrect signals, prompting the computer to continuously increase fuel injection. It could also be due to the idle control valve sticking in the open position, allowing too much air to enter. Having worked with cars for a long time, I know that minor air leaks in the intake system or carbon buildup can disrupt the system’s balance. Using a simple diagnostic tool to read error codes can quickly pinpoint the issue. Regularly keeping the throttle body clean and replacing a faulty sensor can often reset the computer’s logic. This approach is both safe and fuel-efficient; otherwise, prolonged high-idle operation worsens emissions and increases costs.

[DiHaven]

New drivers can be really confused when encountering high idle speed in winter that doesn't drop even after the engine warms up. It's normal for idle speed to be slightly higher during cold starts to help warm up the engine, but it should return to normal once operating temperature is reached. If it doesn't decrease, it's likely due to a faulty sensor or carbon buildup in the engine system. Don't attempt DIY repairs that might cause damage - just drive to a reputable repair shop for inspection. Professional technicians will check the wiring or clean the throttle body to resolve the issue and stabilize idle speed. Remember, regular maintenance can prevent such problems.

[Ora]

High idle speed that doesn't drop poses significant safety hazards during winter driving. I've experienced it myself – fuel consumption surged by over 30% and the engine sounded abnormal. The causes are usually either carbon buildup jamming the throttle body or faulty temperature sensors causing ECU misjudgment. Once idle speed becomes uncontrollable, the increased engine load may lead to overheating damage. It's recommended to immediately check for air leaks in the piping and whether sensor connectors are oxidized causing data transmission errors. Learning to clean the system yourself once will help you understand the issue – proper maintenance can extend vehicle lifespan and save fuel costs.