An o2 sensor is just measuring the amount of oxygen in the exhaust. When the voltage is closer to.1 volts then it is leaner. When it is closer to.9 volts then this is a rich mixture.
The PCM looks at this info and will adjust the injector pulse width to increase or decrease the amount of fuel is being delivered.
Think of o2 sensor data as a health report of what the engine is doing.
Since yours is rich, here are the main causes of rich fuel mixture:
1. Excessive Fuel pressure.
2. Leaking injector.
3. Fuel pressure regulator.
4. EVAP canister is full of fuel.
5. Fuel in crankcase.
6. PCV issue.
7. Excessive blow by.
8. ECM issue.
There are more but they get into the weeds. The other possible cause is faulty o2 sensor but it looks like your engine is actually running rich so I would think we need to go through the other items first.
Monday, June 17th, 2019 AT 1:28 PM