The 1965 Ford Mustang was equipped with either a single-, two- or four-barrel carburetor, depending on the engine option. Each carburetor combines air and gasoline and directs that combination to the engine's cylinders. That combination is determined by an adjustment screw that is set at idle. Fortunately, making the adjustment is fairly straightforward, and a properly adjusted carburetor will help maintain fuel mileage and power.
Position wheel chocks in front of both rear tires.
Apply the parking brake.
Turn the engine on and turn the air conditioning off if the Mustang is equipped with air conditioning.
Place the transmission in "Drive" if equipped with an automatic.
Turn the idle mixture screw on the driver's side of the carburetor either into or out of the carburetor with a screwdriver until the proper idle speed is reached as indicated by the Mustang's tachometer. Turning the screw will change the idle speed. Turn the screw in either direction and note whether the idle speed increases or decreases. If the desired idle speed is not reached by turning the screw in one direction, turn it in the opposite direction. If the Mustang is equipped with an automatic transmission, the idle speed should be 600 revolutions per minute. If the Mustang is equipped with a manual transmission, the idle speed should be 500 RPM.
