Why is the idle speed very high in neutral gear?
3 Answers
Neutral gear idle speed being very high is mainly an issue with the throttle position. There are two or three wire connectors at the throttle; it's possible that one of them is loose, causing poor contact. It is recommended to firmly reconnect them. Neutral gear typically refers to the state where the vehicle's gearshift lever is not engaged in any forward or reverse gear, and the transmission is completely disengaged from the drive wheels. In manual transmissions, neutral is in the middle position, while in automatic transmissions, it is marked with an N. Automatic transmissions do not require the driver to manually shift gears; the vehicle automatically selects the appropriate gear based on driving speed and traffic conditions. Generally, automatic transmission vehicles have six gear positions, from top to bottom: P, R, N, D, S, L.
Having worked in auto repair for so many years, the most common cause of high idle speed in neutral is carbon buildup in the throttle body causing it to stick, or a faulty idle control valve that doesn't open and close smoothly. Vacuum leaks in the intake system can also cause inaccurate air intake measurements leading to this issue. You can check if the air filter is dirty yourself - a clogged filter affects airflow, and if needed, clean the throttle body. Some vehicles experience this due to faulty sensors like the mass airflow sensor reporting incorrect intake data, causing the ECU to compensate by increasing RPM. High idle speed wastes fuel and harms the engine, potentially damaging the catalytic converter over time. Address this promptly for safe driving - normal idle should stabilize between 750-900 RPM. If unsure, have a professional shop scan for trouble codes with a diagnostic tool for accurate diagnosis, saving time from unnecessary guesswork.
A while ago, I noticed my car's idle RPM suddenly surged to over 1200 when in neutral, making unusually loud noises. Initially, I thought it was due to the AC running in hot weather, but the issue persisted even after turning it off, and fuel consumption also increased. After researching online, I learned it might be caused by a faulty throttle position sensor or a stuck idle control valve. Taking it to the repair shop confirmed it was indeed a sensor issue, which was fixed by replacing it for a few hundred bucks. I'd recommend checking if the engine is shaking or if there's any unusual exhaust noise. Sometimes, simply restarting the vehicle can reset the computer. High idle RPM can also lead to excessive emissions, which is bad for the environment. If you're attempting a DIY fix, check the relevant fuses in the fuse box for any that might have blown. Trying a simple replacement could help, but be cautious to avoid causing a short circuit.
