What are the causes of unstable hot idle speed fluctuating between high and low?

1 Answers
McRylee
07/29/25 1:38pm
The causes of unstable hot idle speed fluctuating between high and low are: 1. Oil accumulation and carbon deposits in the throttle body, dirty intake passages; 2. Weak spark due to faulty spark plugs; 3. Fuel system blockages represented by clogged fuel injectors, intake pipe malfunctions; 4. Related sensor failures; 5. Poor valve sealing, intake manifold leaks; 6. Incorrect ignition timing (too early or too late); 7. Improper idle speed adjustment. Solutions for unstable hot idle speed fluctuating between high and low: 1. Clean carbon deposits from the engine and idle speed control valve; 2. Clean the fuel system; 3. Replace spark plugs, high-voltage wires, and ignition coils; 4. Clean the air filter and throttle body; 5. Replace aged engine components.
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