Symptoms of a Faulty Idle Motor?
4 Answers
The manifestations of a damaged idle motor are as follows: 1. Irregular idle speed. One of the most common symptoms associated with a problematic air control valve is irregular idle speed. The idle air control valve is programmed to regulate and maintain the engine's idle speed at a constant rate. If the valve malfunctions or has any issues, it may cause the idle speed to fluctuate. This can result in abnormally high or low idle speeds, or in some cases, repeatedly rising and falling idle speeds. 2. Engine stalling. Another more severe symptom of idle control valve issues is engine stalling. If the idle control valve fails completely, it may leave the vehicle without an air source to maintain proper idling. This can cause the engine to stall while running, and in some cases, may prevent the engine from idling at all, causing it to stall immediately after starting.
The symptoms of my old car's faulty idle control valve were particularly obvious. After starting, the tachometer needle danced erratically between 500 and 1500 RPM. When idling at traffic lights, the car shook like a vibrating phone, accompanied by popping noises from the engine bay. The most troublesome issue was cold start difficulties - I had to press the accelerator to get it started. One day at a highway toll booth, the engine suddenly stalled when I stopped, causing the steering wheel to lock up instantly, nearly causing an accident. The repair shop found the valve stem completely clogged with sludge - cleaning it solved all problems. Fellow drivers, don't hesitate to get it checked if you notice unstable idling.
I've repaired many vehicles with idle speed motor failures and summarized several typical symptoms: unstable idling that fluctuates up and down like panting, RPM dropping instead of rising when the AC is turned on, and severe body shaking. Cold starts are difficult and often require a second ignition attempt, while the engine tends to stall when depressing the clutch after warming up. Some cars may illuminate a warning light on the dashboard, with diagnostic codes indicating idle speed control abnormalities. Don't panic when encountering this situation—first check if the motor connector is loose and clean the throttle body with carburetor cleaner. If the shaking persists after cleaning, it's highly likely that a new motor is needed. This component is most prone to carbon buildup, so it's recommended to clean it every 20,000 kilometers.
The most direct symptom of a faulty idle control motor is abnormal fluctuation in idle speed. When you stop the car and observe the tachometer, the needle will rhythmically jump up and down, with the RPM range reaching 500-2000. The engine sound follows this rhythm, getting louder and softer, like someone gasping for air. It becomes more noticeable when the AC compressor kicks in, with increased body vibration or even sudden stalling. This is mainly caused by motor sticking leading to uncontrolled air intake and imbalanced air-fuel mixture. Older vehicles require special attention - regular throttle body cleaning for cars over eight years old can effectively prevent this. Drivers are advised to pay more attention to tachometer fluctuations when waiting at traffic lights.
