Fuel trims swinging wildly rich at 0° VTC
Posted: Thu Jul 30, 2020 2:24 pm
I have an issue with my fuel trims swinging wildly rich at 0 degrees VTC. Attached are my kal and a log.
Last year I meticulously corrected my fuel maps, such that they were generally within 1-2% in all cells at all cam angles. This summer I've been playing with different cam angles at part throttle, chasing fuel economy. I've noticed that at 0 degrees VTC, something weird happens that I had not observed at 10, 20 or 30 degrees: I can be driving along at a steady speed, and randomly the AFR will begin to drop, to the point that my fuel trims max out and AFR starts swinging rich. I've seen AFR drop by more than 20% with no noticeable changes to any other sensors. However, if I toss it in neutral and blip the throttle, it will return to normal for a few minutes.
In the screenshot below you can observe this.
Is this possibly the evap system feeding fuel vapors? I can't think of anything else that would cause it.
Last year I meticulously corrected my fuel maps, such that they were generally within 1-2% in all cells at all cam angles. This summer I've been playing with different cam angles at part throttle, chasing fuel economy. I've noticed that at 0 degrees VTC, something weird happens that I had not observed at 10, 20 or 30 degrees: I can be driving along at a steady speed, and randomly the AFR will begin to drop, to the point that my fuel trims max out and AFR starts swinging rich. I've seen AFR drop by more than 20% with no noticeable changes to any other sensors. However, if I toss it in neutral and blip the throttle, it will return to normal for a few minutes.
In the screenshot below you can observe this.
Is this possibly the evap system feeding fuel vapors? I can't think of anything else that would cause it.
