What is the idle speed for automatic transmission?

[DeSamantha]

Automatic transmissions generally have an idle speed range between 500 to 850 RPM. During cold starts, the idle speed momentarily reaches around 1500 to 2000 RPM. Once the engine coolant temperature returns to 90 degrees, the idle speed stabilizes within the specified range. Most vehicles maintain an idle speed between 600-850 RPM, with 700-800 RPM being the most common. Below are reasons for unstable idle speed: 1. Leakage in the intake system or vacuum system. 2. Clogged air filter. 3. Malfunctioning idle control valve or auxiliary air valve. 4. Faulty air flow meter. 5. EGR valve stuck open and unable to close. 6. Improper idle adjustment. 7. Low fuel pressure. 8. Poor fuel injector atomization, leakage, or clogging. 9. Faulty spark plugs. 10. Leakage or open circuit in high-voltage wires. 11. Incorrect ignition timing. 12. Low cylinder compression pressure.

[FernandoRose]

The other day I was driving our old Camry and pondered the same thing. When idling in automatic gear, the car moves at a really low speed, around 5 km/h, feeling like a turtle crawling. This speed is controlled by the transmission itself - releasing the brake without pressing the accelerator will make it creep forward slowly. But be careful, it might be even slower when starting a cold engine, and only stabilizes after the engine warms up. If you notice the car suddenly lurching forward faster, it could be due to a dirty throttle body or a stuck idle control valve - better get it checked immediately. Beginners practicing parallel parking especially rely on this creep speed, and once skilled, they can use it for fine-tuning the position.

[LeLane]

When maneuvering my SUV in the underground garage, it basically moves at idle speed, with the speedometer showing between 3-6 km/h. Actually, manufacturers have preset this speed to ensure the engine doesn't stall while preventing the vehicle from creeping too fast. I remember once driving a friend's new car and noticing that the idle speed changed after he modified the tire size – the distance covered per wheel rotation differs. During prolonged traffic jams, it's better to use idle speed crawling instead of constantly pressing the brake to follow the car ahead, as this saves brake pads. If you notice the car jerking forward, it's likely due to carbon buildup causing unstable idle speed, indicating it's time to clean the fuel injectors.

[FelixFitz]

Data measured from three vehicles: The old Sylphy idles at 4 km/h when cold and stabilizes at 6 km/h after warming up; the CR-V maintains 5 km/h regardless of temperature; the Mercedes-Benz C-Class with auto start-stop is slightly faster at 7 km/h. This speed depends on the torque converter slip ratio in the transmission—newer vehicles with fresh fluid perform more smoothly. When stopped at a red light in D gear with the brake pressed, the transmission is under strain, increasing fuel consumption by 0.8 L/h compared to N gear. In northern winters, special attention is needed: at temperatures below -10°C, idle speed may drop to around 2 km/h.

[VanAniyah]

This is a common question from customers during car repairs. Strictly speaking, idle speed refers to the engine's RPM, typically around 700 RPM for regular cars. At this point, the actual speed of the drive wheels can range from 4-7 km/h, which is normal. If the transmission fluid temperature is below 40°C, the speed might be slightly lower, but it will normalize after driving for about ten minutes. If you notice the car jerking when moving at idle speed, first check if the transmission mount bushings are aged or cracked. I've helped adjust cars with ECU tuning before—raising the idle speed to 850 RPM did increase the speed to 9 km/h, but fuel consumption also rose by about 0.5 liters per 100 km, which isn’t cost-effective.

[VanLaila]

When I first started driving, I used to stare at the dashboard all the time. The instructor said not to focus on the exact numbers, just feel if the car could move steadily at a crawl. Later I learned this is related to tire size: after upgrading from the factory 215/55R17 tires to larger rims, the idle speed display might show 8km/h instead of the original 6km/h. Extra caution is needed on rainy slippery roads - once in an epoxy-coated underground garage, my car unexpectedly accelerated to 15km/h with just a light tap on the throttle while idling, nearly causing a rear-end collision. Now when driving with kids in residential areas, I always use idle speed to creep along slowly, which feels much safer than using the accelerator.