Why does the engine speed suddenly increase when stepping on the accelerator?

[LeJocelyn]

This is caused by high idle speed, but the reasons for high idle speed are quite complex. The following are some explanations: 1. Idle switch signal circuit issues: Due to improper adjustment of the idle contact gap, poor contact, damage, or circuit faults, the engine ECU cannot correctly determine the idle condition, leading to idle control errors and various idle speed abnormalities. 2. Idle speed control valve and its circuit issues: When the ISC valve is clogged or stuck due to carbon buildup, or when there are short circuits, open circuits, or grounding in the control circuit, the engine ECU cannot properly control the opening of the ISC valve, resulting in poor idle speed. These should be the focus during diagnosis.