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