How to Lower Excessive Idle Speed?
2 Answers
Ensure there is a gap after fully releasing the throttle grip, install the air filter properly, start the engine and warm it up first, then open the choke. Screw the air adjustment screw all the way in, then reverse it by one turn. Next, adjust the throttle screw to ensure the throttle grip is fully released. Lower the idle speed to reduce the engine RPM as much as possible. Then increase the idle speed, also adjusting the air adjustment screw, to make the engine RPM as high as possible. Repeat these steps several times until you find a satisfactory idle speed.
I've driven a taxi for over 20 years, and high idle speed is a common issue. First, check if the throttle cable is stuck or if there's too much carbon buildup in the throttle body—these are the usual culprits for high idle. For older mechanical throttle bodies, there's an idle adjustment screw under the hood that you can manually turn, but make sure to adjust it when the engine is warm. After adjusting, keep an eye on the tachometer to ensure it doesn't drop below 600 RPM. For modern cars, don't try to fix it yourself—most likely, it's an electronic throttle that needs computer calibration, or issues like an intake leak or a faulty coolant temperature sensor. Once, after adjusting, I noticed fuel consumption skyrocketing, only to find a cracked vacuum hose causing a leak. Adjusting idle speed isn't hard, but the key is identifying the root cause first—otherwise, you might end up with more problems.
