Can't get fuel trims to budge.

[4G63dsmpwr]

Well, I recently wired up my AFC2, and already had my Palm w/MMCD software on it.

I was going through the Tech section, and I was following the instructions on how to adjust your low throttle settings via reading the fuel trims from the logger.

My fuel trim medium is perfect, at 100%, so I didn't want to change anything there.

My fuel trim high, was around 92%, so its not too far off, and I think I can live with that (8% off from exactly 100%).

Now here's my problem, my fuel trim low (which I think is for 0-150Hz of air or something like that) is at 115%. Following the reccomendations from the teck article on tuning an AFC/logger - it shouldn't be any more than 10% away from 100%.

At the 1000RPM point, and the 1600RPM points I added a whole bunch of fuel, started off with little increments, and I couldn't get the fuel trim low to change at all! Even tried it at 40% more fuel at 1000/1600RPM points, and went for a nice long crusie - no change at all.

What would cause the fuel trims to not change at all, even when dumping tons of excess fuel? How long does this usually take, for the ECU to notice a difference?

And how does the O2 fuel trim come into affect? Where should that be throughout the low throttle/high throttle settings?

Thanks for any help!

 

[DSM90AWD]

The High Trims take a bit longer to update than the Low/Mid in my experience. If you want to test if your settings are good.. you can always re-set your ECU (disconnect the battery for 10mins) which will reset your trims to 100%.

Datalogging Oxy-Feedback at a steady cruise speed (70mph) is what I like to do. When trims are perfect.. it should oscillate centered on 100% (i.e. 90% to 110%).. which = 100% on HI fuel trim.

There is a good article explaining the various theories on the ECU /Fuel Trims and Piggy-Back computers here:

http://www.dsmtuners.com/forums/showthread.php?t=58403