How to Adjust the Idle of a 1991 Chevyby Russell Wood
The idle speed on a 1991 Chevrolet refers to the RPM of the engine when the transmission is in drive, and the engine is running, like at a stop light. Sometimes, the idle speed drops too low, and the engine could stall while you're stopped. Other times, the idle speed could be too high, causing the engine to spend more gas than usual. You can adjust the idle speed to the factory specifications, or to your personal preference.
Put the wheel chocks around the front wheels of the Chevrolet and set the parking brake. Pop the hood and take off the air cleaner on the engine by taking off the factory wingnut with your hands and setting the air cleaner away from the engine bay.
Have your assistant start the engine. Let the engine get to normal operating temperature. Locate the throttle cable linkage, which is on the driver's side of the carburetor, just below the bowl where the air cleaner mounts. Locate the adjusting screw, which is just above the throttle linkage. Locate the vehicle specifications sticker, which is on the underside of the hood, and lists the factory idle speed setting.
Tighten down the adjusting screw on the throttle cable linkage with the flathead screwdriver to raise the idle speed, and loosen the screw to lower the idle speed. Have your assistant call out the RPMs listed on the tachometer in the dashboard as you adjust until you reach the idle speed that you prefer or that Chevrolet recommends on the underhood sticker.