Weekend Mechanic host Bruce Bonebrake examines common emission problems on a 1998 Jeep Wrangler. After a tailpipe emissions test, he finds the engine is running lean and that there is a fuel leak in the number-2 cylinder injector. The computer also shows an ignition misfire. With that, he replaces the spark plugs and spark plug wires and services the fuel injection system, replacing the injector and "O" rings on the rest of the injectors. He also cleans the throttle body of deposits, and installs a new MAP sensor (Manifold Absolute Pressure), oxygen sensors (which measure the oxygen content of the exhaust) and air filter. Bruce retests the exhaust emissions and also does a gas cap emissions test. The Jeep passes both and Bruce takes it for a test drive.