Q: Vehicle started running rough while driving. Now running/idling rough running rich.

asked by on August 28, 2016

I was driving the other day around 35mph and 2 miles from home, when it suddenly started running rough. Felt like a misfire but was not getting a check engine light. I drove it home. After letting run for a little while, it finally threw a check engine light and gave a P0172 error code. After a couple restarts and quick drive, it then also gave a P0152 code for upstream 02 sensor on passenger side. I replaced sensor with new sensor and vehicle still running rough and rich. Reset codes and after running, got the P0152 code and also now a P0158 code but no P0172. Also get black smoke when revving engine along with black soot on to my driveway. Reading up, it seems it could be leaking fuel injector, fuel pressure regulator, defective new O2 sensor, or something else?

My car has 77000 miles.
My car has an automatic transmission.

Hello. From the symptoms you describe, it would appear that your vehicle is having issues with the oxygen sensors. P0172 is the code for bank 1 being too rich. This can be caused by a wide variety of issues. The other two codes are for the sensors on bank 2, having excessively high voltage.

This may be due to the rich condition, faulty oxygen sensors, or faulty wiring. The black smoke and soot is a result of excessive fuel that is not being properly burned, and exiting the tailpipe as smoke. A few common causes for these symptoms are a bad fuel pump, fuel pressure regulator, or engine management sensor. As engine management systems can sometimes be difficult to diagnose, I would recommend having the rough idling issue inspected by a professional technician.

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