What Causes High Temperature When Driving but Not at Idle?

[VonElizabeth]

The reasons for high temperature when driving but not at idle may include the following: Poor spark plug performance. Vacuum tube leakage. High-voltage wire leakage. PCV valve blockage. Throttle position sensor malfunction. Idle stepper motor failure. Idle control valve malfunction. Abnormal throttle opening. Intake system leakage. Additional relevant information: Unstable idle: During idle operation, the engine shakes with uneven speed. Causes: Blocked idle air orifice, malfunctioning idle device, weak spark in individual cylinder spark plugs, poor valve sealing in certain cylinders, intake manifold leakage, incorrect ignition timing (too early or too late), improper idle adjustment, etc.