thejazzcat Posted October 25, 2017 Share Posted October 25, 2017 Hey all, I have been having an issue with my idle AF learning (1A) sitting between 12-14 percent. The car occasionally runs rough at idle. AF ratio is spot on, so I assume 14 is the highest it needed to go to reach stoich balance. Looking in to why, I noticed that the fuel richness may not be needed because of a vacuum leak, and instead may be the MAF or O2 failing and reporting incorrect values. My reasoning behind this is when I did an ECU reset and watched the learning value - the car idled buttery smooth with a 1% fuel addition, but continued to up the fuel level regardless, eventually reaching original learning 1A values of 12-14 again. Idle steadily got WORSE as the 1A value went up. To me this sounds like the engine really had all the fuel it needed to begin with, but either the front O2 or MAF sensor is reporting more air than is actually running through the system at idle. The only kink in my theory so far is that I would think you'd see increased learning values across the board if the sensors as a whole were failing... my questions are: -Is it possible for one of those two sensors to fail in such a way that it would only be inaccurate at lower airflow levels (I.e idle)? -Is one of those sensors responsible for learning values while another is responsible for reporting the overall AFR (meaning the AFR associated sensor is fine but the other is not)? -Am I thinking along the right lines here, or am I just being a crazy n00b misunderstanding the fueling system? Thanks for the input, everyone! thejazzcat Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
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