OBD II Code P0171

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97 Accord Ex, 2.2L, 4Dr, 158K miles.
I had the check engine light verified using a OBD II scanner and the results came back P0171. I have noticed that the car idles kind of ruff when stopped. My question is do you think it is the MAF or some other ignition problems.

Do you
have the same problem?
Tuesday, May 1st, 2007 AT 3:08 PM

1 Reply

  • 77,150 POSTS

A code P0171 indicates the engine is running lean. This means there is too much air and/or not enough fuel. You can confirm the engine is running lean by looking at Short Term Fuel Trim (STFT) and Long Term Fuel Trim (LTFT). Normally, STFT and LTFT should be plus or minus 5 to 10 from zero. If STFT and/or LTFT are more than about +12, it indicates the engine is running lean. Negative numbers (-12 or more) indicates the engine is running rich.

A lean fuel condition can be caused by:

* Low fuel pressure due to a weak pump or leaky fuel pressure regulator. (Use a fuel pressure gauge to check fuel pressure at idle)

* Dirty fuel injectors. (Try cleaning the injectors)

* Vacuum leaks at the intake manifold, vacuum hose connections or throttle body. (Use a vacuum gauge to check for low intake vacuum)

* Leaky EGR valve. (Check operation of EGR valve)

* Leaky PCV Valve or hose. (Check valve and hose connections)

* Dirty or defective Mass Airflow Sensor (MAF). (Try cleaning the MAF sensor wires or filament with aerosol electronics cleaner. Do NOT use anything else to clean the sensor, and do not touch the sensor wires)

Hope this help

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Tuesday, May 1st, 2007 AT 6:16 PM

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