In the 1960s, the Rochester Quadrajet carburetor was first introduced, manufactured with four barrels instead of the traditional one or two barrels. Over time, carburetors become out of tune and cause the speed of the mechanism to fluctuate. With a few adjustments of the screw, you can fine tune your carburetor to run like new.
Start the vehicle engine and allow it to warm up for five minutes. Leave the transmission in "Park" and apply the parking brake to add extra security.
Locate the idle speed screw on top of the Quadrajet carburetor. Refer to your vehicle's owner manual or the engine bay sticker to find the recommended carburetor speed for your particular model.
Adjust the speed screw with a flathead screwdriver. Turn the screw counterclockwise to increase the engine speed and clockwise to decrease the speed. If you cannot find the ideal carburetor speed for the model, listen for a strong, low humming noise of the engine. Locate the revolutions per minute (RPM) gauge on your dashboard. Keep the idle speed around 900 to 100 RPMs.
Check the carburetor speed again after one to two minutes. Your Quadrajet may fluctuate depending on the condition of the carburetor, so inspecting the speed after several minutes of the first adjustment can make sure it stays within the ideal range.
