When your vehicle runs rich it means that the engine is receiving too much fuel and not enough air.
This can cause a high fuel bill as well as damage to some parts, for example the catalytic converter.
Some of the Cause may be:
1. A MAF sensor that is faulty.
This sensor calculates the amount of air that goes into the engine. Therefore, if the MAF sensor is faulty, it will calculate the wrong amount of air entering the engine, thus adding to much fuel.
2. An Oxygen sensor that is faulty.
If the Oxygen sensor senses that there is a lean mixture, it will alert the ECU (engine control unit) to add more fuel to the next combustion and vice versa. Even if the mixture is the right amount, if the O2 senor is faulty it will pick up either a lean or rich mixture, and send out the wrong message to the ECU.
3. A Faulty Injector
An injector handles the amount of fuel entering the engine, when one injector is not following and working as it should it can cause a rich mixture.
4. A Faulty fuel pressure regulator
This faulty regulator a cause a high fuel pressure which will lead to a rich mixture.
5. A Faulty engine coolant temperature sensor
An engine coolant temperature sensor measures the coolant’s temperature to identify when extra fuel is needed. When the sensor is faulty it will add too much fuel causing a rich mixture.
Some Symptoms may be;
1. The check engine light will be on because the fuel air ratio will be to high.
2. There will be a fuel smell from the exhaust
3. You will be filing your gas tank constantly
4. Your vehicle will have poor engine performance
5. Black smoke from exhaust