So I have seen several threads that mention it but none really talk about it.

What is it, how do you read it, how do you adjust it?

does it apply to the 1uz?


Thanks

 

Based off experience with my 98 GS 300. I have STFT1, LTFT1, STFT2, & LTFT2. Its short term & long term fuel trim for bank 1 & 2. Its based on how much the ECU has to adjust the fuel trim to get the O2s/Air Fuel sensors to read in the correct range. It usualy jumps between +-3%. If the computer reads that the same adjustment is needed for some time it will flip from ST to LT. I read it through a scan tool device I bought off ebay for like $100. The computer adjusts the fuel trim itself. That is why the computer can "learn around" some aftermarket fuel adjustment devices. You modify the fuel trim, and it says hell no. If the sensors read out of ideal range it will adjust on top of your adjustment. Its a battle. And with all that I have no clue if this is also for a 1UZ. I believe it is for all OBD2 vehicles.

 

So if we tune the car to stay near 14.7 under most conditions, then there isnt a need for the ECU to adjust the trim that much, is that correct?

If this is the case then the long term trim becomes less of a challenge?

 

Correct. The long term only acours after a short trim adjustment goes for too long. If you can keep it "ideal" then it "should" not bounce over into long term.