I have an occasional issue that is hard to reproduce, but I got a good log of it today.
It seems to happen when the car has been running less than a minute, and generally when it is warm to hot. I will be cruising through a parking lot, decelerate, then when I pick the pedal back up (barely), I'll get a big "buck".
I was thinking it was an overactive transient accel gain, but this log makes it look like something else:
Buck.jpg
Just prior to the ETC spike:
- ETC TQ is steady at -12 to -10 ft lbs
- Scheduled TQ is stable at 40 ft lb
- Desired load spikes to 0.57 out of nowhere, so ETC follows
- MP0 Inverse table calls for ~0.1 load at this RPM and a 37 ft lb scheduled TQ
- Cold start emissions reduction has dropped spark to -1*
My only guess at this point is that the desired load spike is in response to the spark reduction. But that seems crazy as a commanded 0.57 load corresponds to a scheduled TQ of over 220 ft lbs, over 5 times the amount shown in scheduled torque, not a modest increase because of efficiency compensation.