Q: Positive long term fuel trim.

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Checked long term fuel trims at idle and bank 1 was steady at 4.7 while bank 2 was steady at 3.1 what do these numbers tell me? What should i check?

My car has 165000 miles.
My car has an automatic transmission.

The fuel trim numbers mean that the fuel is leaned out. If the number is at 0, then there is no change. If the numbers go to a positive increase, then the fuel system is leaning out. If the numbers go to a negative decrease, then the fuel system is becoming rich. Lean conditions will cause the engine’s temperature to rise and could be caused by either a loss of fuel pressure or the injectors are not spraying properly. A rich condition will cause the engine to run with a hesitation or have a nasty smell at the tailpipe and could be caused by spark plugs that are fouled out, a fuel injector that is leaking, or a fuel pressure regulator is stuck on high pressure. If you need further assistance with the fuel trim, then seek out a professional, such as one from Your Mechanic, to help you.

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