High Positive Fuel Trims. - Mazda 6 Forums : Mazda 6 Forum / Mazda Atenza Forum
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post #1 of 1 (permalink) Old 03-22-2015, 10:55 PM Thread Starter
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High Positive Fuel Trims.

High Positive Fuel Trim, Lean Warning

The car is running 20+ % positive fuel trim. The MAF is reading high 3 gps at idle (Grams per Second) and it runs fine with fuel trims around +5 to +7. From what I have read, a gps per liter is reasonable. This makes the reading good. But, if it should be higher at idle, please let me know. Also, the one from my 8 reads the same numbers. At higher speed, the trim rises to +22 or greater. Occasionally triggering a P0171 (lean bank 1) or P0174 (lean bank 2) error. Car does not throw CEL, but is darned close. It did when the intake tube cracked at about +22 trim.

Possible Failures:
MAF, unlikely, a very simple device, and the one from the 8 reads the same.
Vacuum Leak, would have to be massive. Should be able to hear it, and it would affect idle, I plugged all the holes on the intake manifold and it did not help. Might want to do it again at high RPM. I was looking for a low RPM leak.
Bad 02 sensors. All I have read says they will increase emissions and reduce economy. Sounds about right for running rich.
Fuel Pump, stats to run out of steam at higher loads?

What else?
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