Do automatic transmission cars have idle speed?
3 Answers
Automatic transmission cars do have idle speed, which refers to the engine running without load. The idle speed of an automatic transmission car is typically around 5-10km/h, depending on the vehicle's idle RPM and overall condition. Automatic transmission gear positions: P (Park) is for long-term parking. R (Reverse) is engaged when the vehicle needs to move backward. N (Neutral) is used when the vehicle is temporarily parked without turning off the engine. D (Drive) is the forward gear - when the gear lever is in D position, the vehicle will automatically shift gears based on throttle opening and speed data. S (Sport) mode makes the vehicle drive more sportily. M (Manual) mode allows the driver to manually shift gears when the lever is in M position. L (Low) is the low-speed gear. Idle speed can be adjusted. It's generally regulated by adjusting the throttle opening size and idle fuel supply. The engine should operate smoothly within the idle range without vibration and maintain good acceleration performance. Note that idle speed adjustment should avoid frequent RPM fluctuations, as this may cause engine wear.
After driving for so many years, of course automatic transmissions have idle speed—it's the minimum engine speed maintained when you're in P or N gear. Simply put, idle speed keeps the engine running while the car is stationary. In neutral, the engine and transmission aren't connected, so the RPM stays around 600 to 800. If you're in D gear holding the brake at a red light, the engine is still idling, just at a slightly higher RPM. I should remind you, regularly checking the engine's idle condition is important. If the idle is unstable or shaking noticeably, it might be due to excessive carbon buildup, a dirty throttle body, or worn spark plugs needing replacement. Additionally, many modern automatic cars have idle stop-start functions to save fuel, but personally, I find this feature annoying in stop-and-go city traffic, and it also requires extra attention to the battery's condition.
As a seasoned auto repair master, I can definitively tell you that automatic transmission vehicles absolutely have idle speed when in P or N gear. During driving, if you encounter traffic congestion and wait with the D gear engaged while pressing the brake, the engine RPM will also remain close to idle speed. However, I must emphasize that during idling, the engine temperature rises, the fan starts operating, and oil pressure remains at a relatively low level. Prolonged idling can contribute to carbon buildup and may lead to excessive exhaust emissions. If you frequently need to wait at traffic lights, it's advisable to shift to N gear, which protects the transmission and saves some fuel. Additionally, the precision of the electronic throttle control system significantly impacts idle stability, so regular throttle cleaning and using high-quality fuel filters are recommended.
