Q: Car is jerking back and forth. P0171 and P0172 codes are on.

asked by on November 01, 2016

Car runs like normal but after a while will begin to struggle jerk back and forth and won't accelerate if I hit the gas pedal then will go and shut off on me and won't turn back on until after a couple of minutes. Car does it every now and then at random times shows the check engine light and shows both codes p0171 and p0172.

My car has 170000 miles.
My car has an automatic transmission.

Hello. These symptoms suggest something is causing big swings in the fuel mixture when this occurs - quite possibly the O2 sensors (pre-catalytic converter - 2 of them). P0171 is a "lean mix" warning, and P0172 is a "rich mix" warning. They may be able to keep the engine within boundaries most of the time, but not all. If the O2 sensors on your Impala are the originals, they are certainly well-used at this point, and should be replaced. I would recommend having an oxygen sensor replacement for the two pre-catalytic converter sensors. If you’d like to have this done, a certified professional from YourMechanic can perform these services at your home or office.

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