How quickly do LTFT's change
Thread Starter
Team Owner
Joined: Mar 1999
Posts: 22,025
Likes: 192
From: At the beach in little Rhody
How quickly do LTFT's change
I am chasing a problem down and it has to do with long term fuel trim. I think I found the problem, but the car threw the code last night a couple of times. When driving in a particular cell, how quickly does the LTFT change? The service manual specifies returning the LTFT to zero but I don't have a way to do this.
Racer
Joined: Sep 2005
Posts: 429
Likes: 0
From: lincoln nebraska
Originally Posted by vettenuts
I am chasing a problem down and it has to do with long term fuel trim. I think I found the problem, but the car threw the code last night a couple of times. When driving in a particular cell, how quickly does the LTFT change? The service manual specifies returning the LTFT to zero but I don't have a way to do this.
Dave
Thread Starter
Team Owner
Joined: Mar 1999
Posts: 22,025
Likes: 192
From: At the beach in little Rhody
Well, I am still chasing down my P0172. It appears to be in certain cells, but bank 1 is pulling more fuel than bank 2. I am going to swap in a new O2, once that doesn't cure it (not convinced it will) I will need to contact the tuner to see if he can look at my fuel tables. I am also thinking about get HPTuners and trying it myself, I don't want to mess with the WOT tune as my tuner has that nailed, but my LTFT's are a little too negative and a few cells appear to be stepping over the threshold and setting the code. Knowing it would take him a lot more time to set these up, it could be a good learning experience for me if only I can convince the boss I won't destroy the car completely 
Safety Car
Joined: Jul 2005
Posts: 4,275
Likes: 4
From: Vancouver WA
Originally Posted by vettenuts
Well, I am still chasing down my P0172. It appears to be in certain cells, but bank 1 is pulling more fuel than bank 2. I am going to swap in a new O2, once that doesn't cure it (not convinced it will) I will need to contact the tuner to see if he can look at my fuel tables. I am also thinking about get HPTuners and trying it myself, I don't want to mess with the WOT tune as my tuner has that nailed, but my LTFT's are a little too negative and a few cells appear to be stepping over the threshold and setting the code. Knowing it would take him a lot more time to set these up, it could be a good learning experience for me if only I can convince the boss I won't destroy the car completely
I'm am new at EFI tuning, but if one bank is richer or leaner than the other bank, then it sounds like it could only be the o2 sensor. Because that's the only sensor that has it's own for each bank. All the other sensors share all 8 cylinders.
You could switch the o2's from one bank to the next and see if the problem follows. But you will have to unplug and switch the wiring too, and not just the sensors on the other exhaust pipe. (You probably already know that, but just in case you didn't)
