How to Reduce High Idle Speed?

[StMaverick]

If the idle speed is high when the engine is cold and returns to normal after the coolant temperature stabilizes, this is a normal phenomenon. If the idle speed remains consistently high (typically between 700-900 RPM for most vehicles), it may be caused by a stuck throttle valve. Both mechanical and electronic throttle valves can become imprecise in their opening due to carbon buildup. Another possible cause is an erroneous signal from a sensor related to the engine's operating conditions, prompting the ECU to increase the RPM. It is best to have the vehicle inspected at a repair shop. Below is an introduction to idle speed: 1. Concept: Idle speed is an operating condition of a vehicle where the engine runs in neutral gear. The engine speed during idle is referred to as the idle speed. The idle speed can be adjusted by modifying the throttle opening size. Idle speed essentially means the engine is "working without load." 2. Principle: Idle speed refers to the engine running without any load, only overcoming the internal friction resistance of its components, without delivering any external power. The minimum RPM required to maintain stable engine operation is called the idle speed, which is one of the five basic operating conditions of an engine. A well-performing engine typically has an idle speed between 550-800 RPM.

[SanMaci]

Having worked on cars for so many years, dealing with high idle speed is quite common. First, check if the throttle body has severe carbon buildup. Turn off the engine, remove the intake pipe, spray it with carburetor cleaner, and wipe it clean. If the idle is still high, inspect the vacuum hoses for leaks, such as cracked or aged tubes. Use a cigarette or a fog machine to see where smoke escapes. A stuck idle control valve can also be an issue—lightly tap or clean it to see if it moves. Another possibility is a dirty mass airflow sensor affecting the signal; spraying some specialized cleaner can restore it. Sometimes, the ECU needs to be reset by disconnecting the negative battery terminal for five to ten minutes and then reconnecting it, allowing the car to relearn the idle speed. During normal driving, high idle increases fuel consumption and emissions, and the engine noise is louder when parked. Regular maintenance can save a lot of hassle. In short, troubleshoot step by step from simple to complex—don’t rush.

[McElliott]

When driving my own car, high idle speed can be quite bothersome. There are several methods to reduce idle speed: the most common is cleaning the throttle body. You can do it yourself by spraying cleaner on the carbon buildup parts, wearing gloves for protection during the operation. If that doesn't work, check if the air filter is clogged or dirty, and try replacing it with a new one. Vacuum leaks are also crucial—inspect whether the pipe connections under the hood are loose. If the idle control motor is faulty, use a diagnostic tool to read the trouble codes for confirmation. High idle speed during cold starts is normal, but if it persists long-term, repairs are needed. After the engine warms up, the idle speed should stabilize around 800 RPM. For safety, check while parked and avoid driving; if high idle occurs while driving, shift to neutral and proceed cautiously. The final recommendation is to visit a professional shop for tool-based diagnostics to prevent damage to other components. Regular oil changes and cleaning can help prevent such issues.

[DelLuna]

I've only had my car for a little over a year, and encountering high idle speed is quite concerning. To bring it down, you can start with basic steps: first, make sure the floor mat isn't obstructing the accelerator pedal; then, turn off the engine and restart to see if it returns to normal. If that doesn't work, check the relevant fuses in the fuse box—replace any that are blown. If the throttle body is dirty, a simple cleaning might help restore normal operation; if you're not comfortable doing it yourself, call for a tow truck or drive directly to a repair shop. High idle speed leads to louder engine noise and higher fuel consumption, so address it promptly to avoid safety risks.