Q: Positive long term fuel trim.

asked by on March 13, 2017

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.

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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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