Is It Normal for Idling to Only Reach 4000 RPM?
3 Answers
This is a normal situation. Here are the relevant details. 1. Under normal conditions: A 1.5-liter displacement car can generally rev up to 5000 to 6000 RPM during idling, unless the vehicle's computer program is set to limit it to a maximum of 4000 RPM. There is no issue in actual driving, and this is considered normal. During regular driving, the engine speed is mostly between 1500 and 2500 RPM. 2. Internal reason: Vehicles are typically equipped with an idling protection function. The absence of this function would be abnormal. A 1.5-liter displacement engine should at least be able to rev up to around 6000 RPM during idling.
I've been driving for over a decade and have also encountered situations where the engine could only rev up to 4000 RPM in neutral, which I think is quite abnormal. Generally speaking, an engine should be able to easily rev past 6000 RPM in neutral—at least that's been my experience. There could be several reasons: first, the throttle might be too dirty or clogged, restricting air flow into the engine; second, the computer system might be protecting the engine, such as when sensors detect an issue and automatically limit the RPM; third, there could be a problem with the fuel system, like dirty fuel injectors affecting power output. I recommend not delaying the inspection for too long, as it could develop into more serious issues, such as engine weakness during acceleration. It's best to get it diagnosed at a professional repair shop or a 4S dealership—spending a little money for peace of mind is worth it, since safety comes first. Additionally, regular cleaning of intake components can help avoid similar problems, saving both money and hassle.
I'm a DIY car inspection enthusiast, and an idle speed stuck at 4000 RPM isn't normal. From my understanding, modern car ECUs might have protection mechanisms, but such a low limit usually indicates a fault. You can start with simple checks: clean the throttle body for sticking, or inspect if the air filter is clogged with dust restricting airflow. If neither is the issue, it could be an oxygen sensor or throttle position sensor failure. I also recommend trying to disconnect the battery for a few minutes to reset the computer—sometimes this helps. Don't forget to check if any fuses are blown. If the problem persists, visit a professional shop for circuit testing. Don't push it, as engine damage could cost more later.
