What are the symptoms of a faulty idle motor?
4 Answers
The symptoms of a faulty idle motor are: 1. Unstable idle speed; 2. Surging; 3. Vehicle stalling; 4. Delayed acceleration; 5. Engine shaking. The idle motor is primarily responsible for maintaining the car's idle speed, adjusting it based on the engine load during idle conditions. The idle motor is installed on the car's throttle body and regulates the idle air passage area through a stepper motor, controlling the intake air volume of the engine's intake manifold. The intake pressure sensor transmits the detected intake pressure to the computer, which determines the intake volume or engine load, calculates the required fuel injection amount, and controls the engine's idle power.
The most obvious symptom of a faulty idle speed control motor is unstable engine RPM. During cold starts, the tachometer needle jumps erratically, and sometimes the engine suddenly stalls - especially noticeable when waiting at red lights, with the car shaking like a massage chair. When the AC is turned on, the RPM drops instead of rising, and in severe cases, the engine may stall directly, accompanied by the illumination of the check engine light. I once experienced fluctuating idle speeds myself, which turned out to be carbon buildup jamming the throttle valve. These issues should be addressed promptly - sudden stalling at traffic lights is dangerous and increases fuel consumption while damaging the engine. If abnormalities are detected, it's recommended to first read the trouble codes and try cleaning carbon deposits from the throttle body.
I often encounter cars with idle speed motor failures during repairs. The main symptoms are unstable idle speed fluctuations, noticeable engine shaking, or even stalling. The most typical scenario is when the air conditioning compressor kicks in—the engine speed should automatically increase, but instead, it drops or even stalls. Difficulty starting a cold engine is also a red flag, especially in winter when it struggles to start, coughing like it has asthma before finally firing up. Other issues include stalling while coasting in neutral and weak acceleration when stepping on the gas. Leaving it unrepaired for long can lead to increased fuel consumption and dangerous sudden stalls at intersections while waiting for the light.
The most annoying thing about a faulty idle motor is the constant shaking of the car. After starting, the tachometer needle fluctuates wildly, and when stopping at a red light, it feels like the whole car is convulsing. It's even more noticeable when the AC is on—the car struggles to breathe and is prone to stalling as soon as the compressor kicks in. Prolonged issues can also trigger the engine warning light, and cold starts take noticeably longer. I've experienced this problem with my previous car; upon disassembly, it was found that the valve plate was stuck, causing the intake air control to fail. It's advisable to address this promptly to avoid affecting daily driving.
