Skip the auto shop - Our mechanics make house calls

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

asked by on

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.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!
  1. Home
  2. Questions
  3. Vehicle started running rough while driving. Now running/idling rough running rich.

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Truck has no power all accessories dead no light radio no power on daschboard

Yes, in view of the sequence you are reporting, the charging system should be fully checked out. If the battery is new and charging system output turns out to be within specifications, the only reason a battery will discharge is...

Q: My 98 accord keeps giving me system too rich , i changed the o2 sensors both of them , the map sensor, the distributer , spark plu

P0172 means too much fuel or, conversely, too little air, is being supplied and thus the air fuel ratio is sub-optimal. Other causes of this code setting, that are not reflected in your list, include a dirty mass air flow...

Q: I get no heat at all nothing works

This may be related to a faulty blower motor or blower motor relay. Occasionally, the blower motor itself will wear out or become faulty working intermittently as the brush contacts inside the motor wear out. The blower motor relay supplies...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...