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Fuel Trim Trouble

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Old 08-30-2006, 07:35 PM
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Default 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
Old 08-31-2006, 08:15 AM
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Anyone?
Old 08-31-2006, 08:23 AM
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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.
Old 08-31-2006, 08:56 AM
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You are absolutely right.......Wow, I guess I'm not as good at multitasking as I thought. I think I will just start over with the VE table.




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