What causes engine to speed automatically even if I do not step on the accelerator?

An engine speeding up automatically without pressing the accelerator can result from several factors, such as a vacuum leak, which allows excess air into the intake, causing a higher idle speed. Another possibility is a malfunctioning throttle position sensor that incorrectly signals the engine control unit to increase power. Additionally, issues with the idle air control valve can disrupt the airflow, leading to unintended acceleration. Lastly, sticking or malfunctioning throttle cables can also lead to this problem.