Originally Posted by downwardspiral
I re-read your original post a couple times too lol.. That is strange, and it does seem as though the higher the positive LTFT value, the more fuel is added. But I am pretty confused now myself after reading a couple posts on mercedes forums saying contrasting things. However, I did notice a couple places saying trims should not exceed +/- 10%.. and that trim issues tend to be connected to O2 sensor or MAF issues. Assuming positive means more fuel.. If your MAF was dirty the heated element would stay hot, especially when the air in the intake track is moving slowly.. leading the engine to beleive less air is entering it.. So less fuel would be injected. If the engine is in closed loop, and 14.7 is desired, the amount injected would not be enough and the trim would increase to compensate. Once the car was in motion and under load, the increased air velocity would theoretically cool the sensor and the trim would decrease. I am thinking of it like a car overheating in traffic due to the radiator being deprived of moving air.
Great troubleshooting but the SRT has no MAF. It takes throttle position and MAP to calculate air flow. Speed density.