Rich Fuel Condition
A rich fuel condition will result in a faulty catalytic converter. This is because unburned fuel is entering the catalytic converter, and then burning. This will result in damage to the substrate and sulfur like odor emitting from the tailpipe. A rich air fuel ratio causes damage, melting the catalytic converters substrate.
Oxygen and Air Fuel Sensors: A faulty oxygen sensor will cause an engine to run rich. Use a scan tool to read the oxygen sensor output. An oxygen sensor or O2 sensor sending a corrupt signal to the engine control module will result in a rich fuel condition. Symptoms of a rich fuel condition include black exhaust, fouled spark plugs, and poor engine performance.
Fuel Pressure Regulator: A fuel pressure regulator provides a constant fuel pressure to the fuel injectors. A traditional regulator contains a vacuum operated diaphragm. It’s controlled by manifold vacuum that varies pressure to compensate for increased or decreased demand. As the driver accelerates pressure in the intake manifold drops. It provides increased fuel pressure for the increased demand. Electronic regulators do the same thing with more precise computer control.
Fuel Injectors: Fuel injectors are electromechanical devices that atomize pressurized fuel from the fuel rail. They become clogged with deposits that form as fuel dries in the hot tip after engine shutting down. In time and a fuel injector cleaning becomes necessary. A clogged injector results in lean misfire and unburned fuel flowing into the exhaust system. This fuel overheats and damages the catalytic converter. They can also leak or drip fuel. This condition can be diagnosed with a fuel pressure kit and a leak down test.
Engine Coolant Temperature Sensor: The ECT sends a voltage signal to the engine control unit regarding engine temperature. This signal changes as the engine’s coolant temperature changes. If the sensor sends a false reading indicting a cold engine, the ECM will enrich the fuel ratio to compensate. This will cause a rich fuel condition and effect the automatic transmission's torque converter clutch (TCC).