Why Does A Car Have a High Idle
Download The Toyota Idle PDF For Full Analysis
Some of the strange behavior we experience with our vehicles can be explained by the systems that operate according to temperature, speed, and other variables.
For example, when you start your vehicle in the morning you may notice that while it’s cold engine idles a bit higher. This is all calibrated by the engine management system which takes inputs from multiple sensors to determine the point in which temperature has reached acceptable levels.
Idle Warms Up Fluid To Protect
The transmission, for example, has a lot of moving parts in it and relies on the fluid to minimize wear and engage smoothly. As the engine warms up, the fluid warms up to the temperature in which it operates as designed.
In some vehicles, and idle air control (IAC) slightly opens and closes the throttle blades to produce the target RPM.
Why Cars Can Experience An Idle Surge or High Idle
Modern technology in today’s automobiles can cause engine rpm to increase slightly without warning, but don’t panic. There’s a reason for this and once you understand why, you won’t be surprised when it happens.
Here are a few examples of these common occurrences from the experts at Toyota:
Cold start idle-up
An increase in engine idle speed normally occurs just after a cold start on the first drive of the day. This high idle speed is a normal condition of a cold engine. The engine idle speed will reduce as the engine warms up.
Transmission shift
When accelerating while driving at a slow to moderate speed, the driver may experience a slight pause, as the transmission downshifts to a lower gear, followed by a notable increase in engine rpm as the vehicle accelerates.
Catalytic converter protection
On some manual transmission models, the engine control computer may keep the engine rpm above idle as the driver shifts between fifth and sixth gears at highway speeds. This momentary rpm increase is designed to enhance the life of the catalytic converter.
Air conditioning idle-up
On vehicles with an engine-driven A/C compressor, the engine idle rpm will increase slightly as the compressor cycles on. This is done to reduce the chance of an engine stall condition due to the increased load being place on it by the operation of the A/C compressor.
Power steering idle-up
On vehicles with engine-driven hydraulic power steering, the driver will note a slight increase in engine idle rpm when the steering wheel is turned while stopped or at low speeds. This is a normal operating condition and is done to reduce the chance of an engine stall due the increased load placed on it by the operation of the power steering pump.
[source: Toyota Newsroom]
