Idling 1994 Toyota Corolla Gli

I have a problem with my car’s idling. Every morning the idling goes down instead of going up. What could be the cause of it?

RESPONSE

Under normal circumstances the engine idle would go up when first started with a cold engine. This happens because the engine has an ECT (Engine Coolant Temperature) Sensor that lets the engines computer know the engine is cold. When the ECT reads cold it will increase the amount of fuel. As the engines temperature increases the it may reduce the amount of fuel. So what does this mean? If the ECT is stuck or giving a false reading the engines computer may think it is already warm.