What is idle?

idle stop solenoid

Glossary “idle stop solenoid” Definition:
Electromagnetic device mounted on the carburetor linkage that maintains the proper throttle opening for specified idle speed while the ignition is on, but allows the throttle to close further when the ignition is switched off, reducing the amount of air that can enter the engine and the likelihood of dieseling.

idle speed adjustment

Glossary “idle speed adjustment” Definition:
The idle speed on carbureted engines without computer idle-speed control is set by turning a screw that opens or closes the throttle plates. On fuel-injected engines without computer idle-speed control, idle speed is set by turning an idle-air bypass screw that allows air to bypass the throttle plates. Idle speed is not adjustable on engines with computer idle-speed control.

idle mixture adjustment

Glossary “idle mixture adjustment” Definition:
An adjustment made on carbureted engines by removing the antitampering plugs and turning the idle-mixture screws until the proper idle mixture is achieved. Setting the idle mixture on an emissions-controlled engine may require monitoring exhaust CO or using a special procedure called propane enrichment.

idle limiter cap

Glossary “idle limiter cap” Definition:
A plastic device pressed over a carburetor’s idle-mixture screw that limits the amount of adjustment during service to help eliminate excessive air pollution that is caused if the mixture is too rich.

idle air-control valve

Glossary “idle air-control valve” Definition:
An electrically operated valve that, on commands from the engine-control computer, varies the size of an air passage that bypasses the throttle plate of an electronic fuel-injection system, thus controlling idle speed.