High Idle Causes
High Idle Causes A high idle in your car can cause you to worry. When the engine seems to rev up on its own while you are at a standstill, you may wonder if it's a sign of trouble that needs the attention of a mechanic. The answer to that question depends on the cause of the high idle. Some causes are harmless, while others can indicate the need for a repair. Faulty Fuses Most modern car engines control the engine idle speed through a motor called an IAC (idle air control) motor. One of the leading causes of IAC motor malfunction is a blown or faulty fuse. A malfunctioning fuse in any of the electronically controlled components including the air bag system can disrupt the function of the IAC motor and lead to a higher idle speed than usual. Computer Malfunctions Computers control a modern car's engine and transmission, its brake system and its airbag system. If the fuses are fine, the computer system itself in one of these components might be malfunctioning....