What is the ideal idle speed for a car?

[MaggieAnn]

Normally it ranges between 700-800 RPM. Below is relevant information about car idle speed: 1. The function of car idle speed: Idle speed is an operational state of a car, referring to the engine running in neutral gear. The engine speed during idle is called idle speed. Idle speed can be adjusted by modifying parameters like throttle opening. Idling means the engine is "producing power without doing work". When the engine is running and the accelerator pedal is fully released, the engine enters idle state. 2. Causes of unstable idle speed: Direct causes refer to mechanical components being dirty, worn, or improperly installed, leading to variations in cylinder power output which creates imbalance among cylinders, resulting in unstable idle speed; Indirect causes refer to abnormalities in the engine's electronic control system causing poor combustion mixture, making it difficult to balance cylinder power output and resulting in unstable idle speed.

[DeLondon]

As an auto repair technician, I believe idle speed issues need to be analyzed based on specific vehicle models. For mainstream cars nowadays, the normal idle speed after warming up usually fluctuates between 700-900 RPM - as long as the needle stays steady, it's fine. It's completely normal for the RPM to spike up to 1200 during cold starts since the ECU is heating up the catalytic converter. Don't panic if the RPM temporarily jumps to around 1000 when the AC is on or during full steering lock. If you notice the tachometer shaking like a vibrating phone or fluctuating like a seesaw at stoplights, it's likely caused by carbon buildup in the throttle body that needs cleaning. Remember not to rev the engine aggressively right after ignition - it's really bad for the car.

[SanAliyah]

Having driven for fifteen years, I've noticed that every car's idle speed is truly different. My old Toyota runs steadily at 600 RPM when warmed up, but my wife's domestic SUV needs 800 RPM to stop shaking. The key is to observe whether the RPM stabilizes after the coolant temperature gauge reaches the midpoint—it's common to see 1200 RPM when starting a cold engine in winter. The worst is when the RPM suddenly drops below 500 at a red light, causing the whole car to shudder—that's a sign to immediately check the spark plugs and ignition coils. Some car enthusiasts experience unstable idle after installing high-power headlights, which usually indicates the alternator can't handle the voltage demand.

[KarterMarie]

When I was learning to drive, the instructor said just watching the tachometer was enough. After warming up, the needle usually settles at 750 RPM for new cars, but tests show it can rise to around 850 RPM with the AC on. It's normal for the engine to sound louder and run at higher RPM during cold winter mornings—just wait two minutes until the blue light goes off, and the RPM will drop on its own. German cars tend to have higher idle speeds, especially turbocharged models, usually staying above 800 RPM. If you notice the RPM suddenly dropping to 500 while driving, don’t hesitate—head straight to the repair shop, as it could indicate a faulty sensor.