Q: My check engine light is on reading code po171 lean

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My check engine light is on reading a code of po171 lean. Sometimes when I accelerate it hesitates like if your riding a horse or in a boat swaying front to back but this rarely happens but it still happens. I also have some kind of fluid I believe to be oil coming down and covering the bottom of my engine. No other problems besides lack of alot of power when accelerating and that oil on the bottom. I also just replaced the mass flow sensor and got an oil change. Any thoughts?

My car has 171000 miles.
My car has an automatic transmission.

A: The <a href='https://www.yourmechanic.com/a...

The code P0171 is for the engine control module is getting an O2 sensor lean bank 1 problem in the engine and has tried to compensate by making the injection system go rich on that bank. There is a long list of possible causes like intake bolts loose, injectors sticking, vacuum leaks, clogged injectors, carbon buildup on injectors or valves. The list goes on. You will need to have the pinpoint test performed to diagnose the problem and code to see if there is a sensor issue or a problem with another engine component. The oil leaking may have got on the O2 sensor and caused a bad reading. If this is the case, then the oil leak and O2 sensor will need to be repaired. I recommend having a mechanic come to your home or office to give the Check Engine Light a thorough inspection to ensure appropriate repairs are made.

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