Fuel Trim Trouble
Fuel Trim Trouble Tuning the car in my sig. Done a few rounds of LTFT tuning. Highest LTFTs in that log were real close (-5 or -6), I put that table into the spreadsheet and adjusted the Primary and Secondary VE tables. Downloaded program, reset trims, put about 75 miles on it before I tore into the engine to swap the oil pump and timing chain.
The battery was disconnected for about 9 days while a chipped away at the engine mods. Fired it back up with fresh oil and fresh coolant on Sunday. Put another 75 miles on it before I started scanning. At this point, the car feels incredibly strong. I scan it and I'm way off (+20) in almost all my part throttle cells. So i saved the previous tune, changed it according to the the new scan and reset the fuel trims. Only put a few miles on it since I reset the trims, but it feels much more sluggish.
How did my fuel trims get so far off in between scans? Did disconnecting the PCM cause this? I am doing something wrong? I have the MAF set to 0 during scans. The adjustments I made after scan 1 were proportional to the scan.
Thanks,
AW
The battery was disconnected for about 9 days while a chipped away at the engine mods. Fired it back up with fresh oil and fresh coolant on Sunday. Put another 75 miles on it before I started scanning. At this point, the car feels incredibly strong. I scan it and I'm way off (+20) in almost all my part throttle cells. So i saved the previous tune, changed it according to the the new scan and reset the fuel trims. Only put a few miles on it since I reset the trims, but it feels much more sluggish.
How did my fuel trims get so far off in between scans? Did disconnecting the PCM cause this? I am doing something wrong? I have the MAF set to 0 during scans. The adjustments I made after scan 1 were proportional to the scan.
Thanks,
AW
Sounds like you might have added the negative # to the VE instead of multiply by percentage??? I'd go back to the previous tune and start again. If it was within -5~-6%, you could disable LTFT's and tune off of the STFT averages. If all of the cells were -5~-6%, I'd just multiply the cells by .98 (-2%) and call it quits. Check it with the log and make sure LTFT's are still slightly negative. But, -4~-5% is quiting territory if you ask me. 
