A Mazda Rx7 needs adjustments to the carburetor when the vehicle idles at a high speed. High-speed idles are caused by a rich mixture. Too much gas and not enough air in the carburetor produces a rich mixture, and lowers the gas mileage and engine efficiency by not fully combusting the fuel. A fast idle is often accompanied by the smell of gasoline in a car. Adjusting the fast idle screw properly will correct these symptoms.
Park the vehicle and turn the ignition off. Open the hood and let the Rx7 cool down completely.
Turn the wing nut counterclockwise on top of the air filter cover to loosen it. Pull the cover straight up and off. Pull the air filter straight up and out of the cleaner housing.
Grasp the hose on the left side of the air cleaner housing with one hand and the housing's metal tail on the left with the other hand. Wiggle the housing and hose to detach the hose. Pull the housing straight up to reveal the carburetor.
Put on safety glasses.
Spray a liberal amount of carburetor cleaner in the top of the opening. The carburetor is a round metal tube open on the top with a butterfly valve that opens and closes to admit or restrict air to the component.
Start the car and listen to the idle speed. Locate the fast idle adjustment screw on the right side of the carburetor. The screw has a linkage that attaches to it and leads into the driver's side firewall for the gas pedal to apply pressure and add gas to the engine. Push the linkage connected to the screw towards the firewall. The engine will receive additional gas and increase in RPMs.
Insert a flat screwdriver into the idle adjustment screw. Turn the screw counterclockwise by small increments of one-quarter turns to lower the fast idle. If the car dies or sputters, turn the screw slightly clockwise to increase the idle speed.
Replace the air filter housing on the carburetor and press the air duct hose on the left into the metal tail.
Blow the air filter off from the inside of the circle to the outside with an air compressor to remove any dust. Place the air filter in the housing. Replace the cover and tighten the wing nut clockwise.
